Thomas is right. "last" should unambiguously mean ***last**.* If authors want to ascertain the second-last, or third-last, a different method is probably preferable. "nth" sounds great, and could work from the end of the array if passed a negative value.
This would circumvent the issues raised by overriding the -1 property a.l.a Python. On 23 January 2016 at 17:04, <[email protected]> wrote: > Send es-discuss mailing list submissions to > [email protected] > > To subscribe or unsubscribe via the World Wide Web, visit > https://mail.mozilla.org/listinfo/es-discuss > or, via email, send a message with subject or body 'help' to > [email protected] > > You can reach the person managing the list at > [email protected] > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of es-discuss digest..." > > Today's Topics: > > 1. Re: JavaScript Language feature Idea (kdex) > 2. Re: JavaScript Language feature Idea (Thomas) > 3. Re: JavaScript Language feature Idea (/#!/JoePea) > > > ---------- Forwarded message ---------- > From: kdex <[email protected]> > To: [email protected] > Cc: > Date: Sat, 23 Jan 2016 06:40:28 +0100 > Subject: Re: JavaScript Language feature Idea > While John's solution doesn't run into conflicts with downward > compatibility, > it still wouldn't solve the problem of getting the n-th last element of an > array. To solve this, it'd probably be a good idea to extend the prototype > and > specify a parameter, defaulting to 1. > > `Array.prototype.last` doesn't show up a terrible lot on search engines, > either, so we might actually be lucky here. Other than that, I also found > two > more threads[1][2] on the EcmaScript discussion archives that propose it. > > They might be worth a read. > > [1] https://esdiscuss.org/topic/array-prototype-last > [2] https://esdiscuss.org/topic/proposal-array-prototype-last > > On Samstag, 23. Januar 2016 15:44:19 CET John Gardner wrote: > > Using a well-known symbol to access an array's last element is probably > > wiser than a typical method or property: > > > > let a = [0, 1, 2, 3]; > > console.log( > > a[Symbol.last] === 3 > > /* true */ > > ); > > > > There're obviously instances where authors have extended Array prototypes > > with "last" methods or properties, but we can't guarantee they'd all work > > the same. For instance, assume there are some implementations that skip > > undefined values: > > > > var a = [0, 1, 2, undefined, undefined]; > > Array.prototype.last = function(){ > > return this[this.length - 1]; > > }; > > /** One that skips undefined values */ > > Array.prototype.last = function(){ > > var offset = 1; > > while(offset < this.length && undefined === this[this.length - offset]) > > ++offset; > > return this[this.length - offset]; > > } > > > > These discrepancies are subtle, but have the potential to break backwards > > compatibility. > > > > Using a well-known symbol eliminates the potential for conflict. > > Furthermore, it also offers an opportunity to complement any iterable > > object's ability to synthesise array-like behaviour. For instance, it > > enables iterables to also return the last object in their list of values: > > > > let pruebas = { > > data: ["Probando", "la", "mierda", "esta", undefined], > > > > [Symbol.iterator](){ > > /* Stuff with .data */ > > }, > > [Symbol.last](){ > > /** Stuff to skip undefined values or whatever */ > > let offset = 1; > > let data = this.data; > > while( > > offset < data.length && > > undefined === data[data.length - offset] > > ) > > ++offset; > > return data[data.length - offset]; > > } > > } > > > > On 23 January 2016 at 08:36, <[email protected]> wrote: > > > Send es-discuss mailing list submissions to > > > > > > [email protected] > > > > > > To subscribe or unsubscribe via the World Wide Web, visit > > > > > > https://mail.mozilla.org/listinfo/es-discuss > > > > > > or, via email, send a message with subject or body 'help' to > > > > > > [email protected] > > > > > > You can reach the person managing the list at > > > > > > [email protected] > > > > > > When replying, please edit your Subject line so it is more specific > > > than "Re: Contents of es-discuss digest..." > > > > > > Today's Topics: > > > 1. Re: Javascript Language feature Idea (Bradley Meck) > > > 2. Re: Re: Javascript Language feature Idea (Alican ?ubuk?uo?lu) > > > 3. Re: Javascript Language feature Idea (kdex) > > > 4. Re: Javascript Language feature Idea (kdex) > > > 5. Re: Javascript Language feature Idea (Benoit Marchant) > > > > > > ---------- Forwarded message ---------- > > > From: Bradley Meck <[email protected]> > > > To: Dmitry Soshnikov <[email protected]> > > > Cc: es-discuss <[email protected]> > > > Date: Fri, 22 Jan 2016 13:51:54 -0600 > > > Subject: Re: Javascript Language feature Idea > > > Personally I prefer a well known symbol for marking you are grabbing > from > > > the end of the list rather than this wrapping behavior like D ( > > > https://dlang.org/spec/arrays.html#array-length ). That said I think > > > `.last` is more reasonable than changing prototypes. > > > > > > On Fri, Jan 22, 2016 at 1:17 PM, Dmitry Soshnikov < > > > > > > [email protected]> wrote: > > >> On Fri, Jan 22, 2016 at 9:53 AM, RacerD123 <[email protected]> > wrote: > > >>> In other programming languages such as python, you can specify the > last > > >>> element of a list with "list[-1]" but in javascript you have to do > > >>> "list[list.length-1]". Is there maybe a way to make this feature in > > >>> javascript? > > >> > > >> This could be a good addition, although `slice` may work as well. This > > >> has been discussed previously as well in the last 4-5 years. In > addition > > >> with non-enumerable properties you can just monkey-patch > > >> `Array.prototype` > > >> with the `peek` or `last` method. I guess approach when some library > > >> forces > > >> some method to widely used, can be a good candidate for adding it to > the > > >> spec (this how it was with `Function.prototype.bind`, e.g., although > > >> today > > >> monkey-patching is a bad practice of course). > > >> > > >> In addition, you can monkey-patch just `-1`, and other indexes, e.g. a > > >> gist from 5 years old, when a similar topic was proposed here: > > >> https://gist.github.com/DmitrySoshnikov/984921 > > >> > > >> Dmitry > > >> > > >> _______________________________________________ > > >> es-discuss mailing list > > >> [email protected] > > >> https://mail.mozilla.org/listinfo/es-discuss > > > > > > ---------- Forwarded message ---------- > > > From: "Alican Çubukçuoğlu" <[email protected]> > > > To: [email protected] > > > Cc: > > > Date: Fri, 22 Jan 2016 22:32:42 +0200 > > > Subject: Re: Re: Javascript Language feature Idea > > > More cool stuff: > > > ```javascript > > > const arr = [1, 2, 3]; > > > > > > // Easy push > > > arr[] = 4; // => arr[arr.length]; > > > > > > // Easy s(p)lice > > > arr[begin, end];, > > > arr[begin,]; // => arr[begin, arr.length]; > > > arr[begin, end] = [1, 2, 3]; > > > ``` > > > > > > A terrible example (terrible because this should be done with WebGL > > > shaders): > > > ```javascript > > > const image = [ /* Umbagajillion of RGBA pixels */ ]; > > > > > > function manipulate(rgba) { > > > > > > rgba[0] += 10; > > > rgba[1] += 10; > > > rgba[2] += 10; > > > > > > } > > > > > > for (let i = 0; i < image.length / 4; i++) { > > > > > > const begin = i * 4; > > > const end = begin + 4; > > > > > > /* > > > > > > In case easy s(p)lice doesn't actually Array.p.slice > > > and just creates a limited view of the array > > > without breaking reference > > > (image[begin, end] === image[begin, end]) > > > > > > */ > > > manipulate(image[begin, end]); > > > > > > /* > > > > > > In case easy s(p)lice does Array.p.slice > > > and creates a new array > > > (image[begin, end] !== image[begin, end]) > > > > > > */ > > > const pixel = image[begin, end]; > > > manipulate(pixel); > > > image[begin, end] = pixel; > > > > > > } > > > ``` > > > > > > > > > ---------- Forwarded message ---------- > > > From: kdex <[email protected]> > > > To: [email protected] > > > Cc: > > > Date: Fri, 22 Jan 2016 22:00:01 +0100 > > > Subject: Re: Javascript Language feature Idea > > > I really adore the slicing syntax. Just as a quick fix, though, > > > > > > > arr[begin,]; // => arr[begin, arr.length]; > > > > > > should obviously return `arr[begin, arr.length - 1]`. > > > > > > Honestly, I'm not too sure if the "easy push" syntax is particularly > self- > > > explanatory. There might be better alternatives. > > > > > > On Freitag, 22. Januar 2016 22:32:42 CET Alican Çubukçuoğlu wrote: > > > > More cool stuff: > > > > ```javascript > > > > const arr = [1, 2, 3]; > > > > > > > > // Easy push > > > > arr[] = 4; // => arr[arr.length]; > > > > > > > > // Easy s(p)lice > > > > arr[begin, end];, > > > > arr[begin,]; // => arr[begin, arr.length]; > > > > arr[begin, end] = [1, 2, 3]; > > > > ``` > > > > > > > > A terrible example (terrible because this should be done with WebGL > > > > shaders): > > > > ```javascript > > > > const image = [ /* Umbagajillion of RGBA pixels */ ]; > > > > > > > > function manipulate(rgba) { > > > > > > > > rgba[0] += 10; > > > > rgba[1] += 10; > > > > rgba[2] += 10; > > > > > > > > } > > > > > > > > for (let i = 0; i < image.length / 4; i++) { > > > > > > > > const begin = i * 4; > > > > const end = begin + 4; > > > > > > > > /* > > > > > > > > In case easy s(p)lice doesn't actually Array.p.slice > > > > and just creates a limited view of the array > > > > without breaking reference > > > > (image[begin, end] === image[begin, end]) > > > > > > > > */ > > > > manipulate(image[begin, end]); > > > > > > > > /* > > > > > > > > In case easy s(p)lice does Array.p.slice > > > > and creates a new array > > > > (image[begin, end] !== image[begin, end]) > > > > > > > > */ > > > > const pixel = image[begin, end]; > > > > manipulate(pixel); > > > > image[begin, end] = pixel; > > > > > > > > } > > > > ``` > > > > > > ---------- Forwarded message ---------- > > > From: kdex <[email protected]> > > > To: [email protected] > > > Cc: > > > Date: Fri, 22 Jan 2016 22:14:20 +0100 > > > Subject: Re: Javascript Language feature Idea > > > Standardizing unused array keys breaks compatibility about as much as > > > extending the prototype does, really. Users can already mangle with > both. > > > > > > The problems are a little more subtle, and yes, it would severely break > > > backwards compatibility. Consider this example (accessing an element > based > > > on > > > a computed index): > > > > > > ```js > > > let a = [1, 2, 3]; > > > let occurrence = a.indexOf(4); > > > a[occurrence]; > > > ``` > > > > > > Currently, this should result in `undefined`. After your proposal, you > > > could > > > introduce a potential bug into every program that accesses arrays > using an > > > index computed with `Array.prototype.indexOf`, since it would now > return > > > `3`. > > > > > > On Freitag, 22. Januar 2016 18:59:06 CET Sander Deryckere wrote: > > > > Since Array inherits from Object, it can have any key, including the > key > > > > "-1". So something like list[-1] would break compatibility as users > can > > > > > > now > > > > > > > already assign values to the index -1. > > > > > > > > If you want a short way to access the last element, it should > probably > > > > > > be a > > > > > > > function in the Array prototype. Something like list.last(). > > > > > > > > Regards, > > > > Sander > > > > > > > > 2016-01-22 18:53 GMT+01:00 RacerD123 <[email protected]>: > > > > > In other programming languages such as python, you can specify the > > > > > last > > > > > element of a list with "list[-1]" but in javascript you have to do > > > > > "list[list.length-1]". Is there maybe a way to make this feature in > > > > > javascript? > > > > > > > > > > _______________________________________________ > > > > > es-discuss mailing list > > > > > [email protected] > > > > > https://mail.mozilla.org/listinfo/es-discuss > > > > > > ---------- Forwarded message ---------- > > > From: Benoit Marchant <[email protected]> > > > To: kdex <[email protected]> > > > Cc: [email protected] > > > Date: Fri, 22 Jan 2016 13:35:55 -0800 > > > Subject: Re: Javascript Language feature Idea > > > Interesting! More pedestrian, it would be nice to finally have a > version > > > of splice that doesn't create a new other Array as a side effect. > > > > > > > On Jan 22, 2016, at 13:00, kdex <[email protected]> wrote: > > > > > > > > I really adore the slicing syntax. Just as a quick fix, though, > > > > > > > >> arr[begin,]; // => arr[begin, arr.length]; > > > > > > > > should obviously return `arr[begin, arr.length - 1]`. > > > > > > > > Honestly, I'm not too sure if the "easy push" syntax is particularly > > > > > > self- > > > > > > > explanatory. There might be better alternatives. > > > > > > > >> On Freitag, 22. Januar 2016 22:32:42 CET Alican Çubukçuoğlu wrote: > > > >> More cool stuff: > > > >> ```javascript > > > >> const arr = [1, 2, 3]; > > > >> > > > >> // Easy push > > > >> arr[] = 4; // => arr[arr.length]; > > > >> > > > >> // Easy s(p)lice > > > >> arr[begin, end];, > > > >> arr[begin,]; // => arr[begin, arr.length]; > > > >> arr[begin, end] = [1, 2, 3]; > > > >> ``` > > > >> > > > >> A terrible example (terrible because this should be done with WebGL > > > >> shaders): > > > >> ```javascript > > > >> const image = [ /* Umbagajillion of RGBA pixels */ ]; > > > >> > > > >> function manipulate(rgba) { > > > >> > > > >> rgba[0] += 10; > > > >> rgba[1] += 10; > > > >> rgba[2] += 10; > > > >> > > > >> } > > > >> > > > >> for (let i = 0; i < image.length / 4; i++) { > > > >> > > > >> const begin = i * 4; > > > >> const end = begin + 4; > > > >> > > > >> /* > > > >> > > > >> In case easy s(p)lice doesn't actually Array.p.slice > > > >> and just creates a limited view of the array > > > >> without breaking reference > > > >> (image[begin, end] === image[begin, end]) > > > >> > > > >> */ > > > >> manipulate(image[begin, end]); > > > >> > > > >> /* > > > >> > > > >> In case easy s(p)lice does Array.p.slice > > > >> and creates a new array > > > >> (image[begin, end] !== image[begin, end]) > > > >> > > > >> */ > > > >> const pixel = image[begin, end]; > > > >> manipulate(pixel); > > > >> image[begin, end] = pixel; > > > >> > > > >> } > > > >> ``` > > > > > > > > _______________________________________________ > > > > es-discuss mailing list > > > > [email protected] > > > > https://mail.mozilla.org/listinfo/es-discuss > > > > > > _______________________________________________ > > > es-discuss mailing list > > > [email protected] > > > https://mail.mozilla.org/listinfo/es-discuss > > > > > > ---------- Forwarded message ---------- > From: Thomas <[email protected]> > To: kdex <[email protected]> > Cc: [email protected] > Date: Sat, 23 Jan 2016 16:51:21 +1100 > Subject: Re: JavaScript Language feature Idea > Is this what you're thinking? > > Array.prototype.nth = function (n){ > if(n < 0){ > return this[this.length -n]; > } else { > return this[n]; > } > } > > Thomas Foster > > @thomasfoster96 > Ph: +61477808008 > http://thomasfoster.co/ > > > On 23 Jan 2016, at 4:40 PM, kdex <[email protected]> wrote: > > > > While John's solution doesn't run into conflicts with downward > compatibility, > > it still wouldn't solve the problem of getting the n-th last element of > an > > array. To solve this, it'd probably be a good idea to extend the > prototype and > > specify a parameter, defaulting to 1. > > > > `Array.prototype.last` doesn't show up a terrible lot on search engines, > > either, so we might actually be lucky here. Other than that, I also > found two > > more threads[1][2] on the EcmaScript discussion archives that propose it. > > > > They might be worth a read. > > > > [1] https://esdiscuss.org/topic/array-prototype-last > > [2] https://esdiscuss.org/topic/proposal-array-prototype-last > > > >> On Samstag, 23. Januar 2016 15:44:19 CET John Gardner wrote: > >> Using a well-known symbol to access an array's last element is probably > >> wiser than a typical method or property: > >> > >> let a = [0, 1, 2, 3]; > >> console.log( > >> a[Symbol.last] === 3 > >> /* true */ > >> ); > >> > >> There're obviously instances where authors have extended Array > prototypes > >> with "last" methods or properties, but we can't guarantee they'd all > work > >> the same. For instance, assume there are some implementations that skip > >> undefined values: > >> > >> var a = [0, 1, 2, undefined, undefined]; > >> Array.prototype.last = function(){ > >> return this[this.length - 1]; > >> }; > >> /** One that skips undefined values */ > >> Array.prototype.last = function(){ > >> var offset = 1; > >> while(offset < this.length && undefined === this[this.length - offset]) > >> ++offset; > >> return this[this.length - offset]; > >> } > >> > >> These discrepancies are subtle, but have the potential to break > backwards > >> compatibility. > >> > >> Using a well-known symbol eliminates the potential for conflict. > >> Furthermore, it also offers an opportunity to complement any iterable > >> object's ability to synthesise array-like behaviour. For instance, it > >> enables iterables to also return the last object in their list of > values: > >> > >> let pruebas = { > >> data: ["Probando", "la", "mierda", "esta", undefined], > >> > >> [Symbol.iterator](){ > >> /* Stuff with .data */ > >> }, > >> [Symbol.last](){ > >> /** Stuff to skip undefined values or whatever */ > >> let offset = 1; > >> let data = this.data; > >> while( > >> offset < data.length && > >> undefined === data[data.length - offset] > >> ) > >> ++offset; > >> return data[data.length - offset]; > >> } > >> } > >> > >> O > > > > ---------- Forwarded message ---------- > From: "/#!/JoePea" <[email protected]> > To: John Gardner <[email protected]> > Cc: es-discuss <[email protected]> > Date: Fri, 22 Jan 2016 22:04:14 -0800 > Subject: Re: JavaScript Language feature Idea > I think Symbol.last seems like the best option so far, without breaking > things. > > On Fri, Jan 22, 2016 at 8:44 PM, John Gardner <[email protected]> > wrote: > > Using a well-known symbol to access an array's last element is probably > > wiser than a typical method or property: > > > > let a = [0, 1, 2, 3]; > > console.log( > > a[Symbol.last] === 3 > > /* true */ > > ); > > > > There're obviously instances where authors have extended Array prototypes > > with "last" methods or properties, but we can't guarantee they'd all work > > the same. For instance, assume there are some implementations that skip > > undefined values: > > > > var a = [0, 1, 2, undefined, undefined]; > > Array.prototype.last = function(){ > > return this[this.length - 1]; > > }; > > /** One that skips undefined values */ > > Array.prototype.last = function(){ > > var offset = 1; > > while(offset < this.length && undefined === this[this.length - offset]) > > ++offset; > > return this[this.length - offset]; > > } > > > > These discrepancies are subtle, but have the potential to break backwards > > compatibility. > > > > Using a well-known symbol eliminates the potential for conflict. > > Furthermore, it also offers an opportunity to complement any iterable > > object's ability to synthesise array-like behaviour. For instance, it > > enables iterables to also return the last object in their list of values: > > > > let pruebas = { > > data: ["Probando", "la", "mierda", "esta", undefined], > > > > [Symbol.iterator](){ > > /* Stuff with .data */ > > }, > > [Symbol.last](){ > > /** Stuff to skip undefined values or whatever */ > > let offset = 1; > > let data = this.data; > > while( > > offset < data.length && > > undefined === data[data.length - offset] > > ) > > ++offset; > > return data[data.length - offset]; > > } > > } > > > > > > On 23 January 2016 at 08:36, <[email protected]> wrote: > >> > >> Send es-discuss mailing list submissions to > >> [email protected] > >> > >> To subscribe or unsubscribe via the World Wide Web, visit > >> https://mail.mozilla.org/listinfo/es-discuss > >> or, via email, send a message with subject or body 'help' to > >> [email protected] > >> > >> You can reach the person managing the list at > >> [email protected] > >> > >> When replying, please edit your Subject line so it is more specific > >> than "Re: Contents of es-discuss digest..." > >> > >> Today's Topics: > >> > >> 1. Re: Javascript Language feature Idea (Bradley Meck) > >> 2. Re: Re: Javascript Language feature Idea (Alican ?ubuk?uo?lu) > >> 3. Re: Javascript Language feature Idea (kdex) > >> 4. Re: Javascript Language feature Idea (kdex) > >> 5. Re: Javascript Language feature Idea (Benoit Marchant) > >> > >> > >> ---------- Forwarded message ---------- > >> From: Bradley Meck <[email protected]> > >> To: Dmitry Soshnikov <[email protected]> > >> Cc: es-discuss <[email protected]> > >> Date: Fri, 22 Jan 2016 13:51:54 -0600 > >> Subject: Re: Javascript Language feature Idea > >> Personally I prefer a well known symbol for marking you are grabbing > from > >> the end of the list rather than this wrapping behavior like D ( > >> https://dlang.org/spec/arrays.html#array-length ). That said I think > `.last` > >> is more reasonable than changing prototypes. > >> > >> On Fri, Jan 22, 2016 at 1:17 PM, Dmitry Soshnikov > >> <[email protected]> wrote: > >>> > >>> On Fri, Jan 22, 2016 at 9:53 AM, RacerD123 <[email protected]> > wrote: > >>>> > >>>> In other programming languages such as python, you can specify the > last > >>>> element of a list with "list[-1]" but in javascript you have to do > >>>> "list[list.length-1]". Is there maybe a way to make this feature in > >>>> javascript? > >>>> > >>> > >>> This could be a good addition, although `slice` may work as well. This > >>> has been discussed previously as well in the last 4-5 years. In > addition > >>> with non-enumerable properties you can just monkey-patch > `Array.prototype` > >>> with the `peek` or `last` method. I guess approach when some library > forces > >>> some method to widely used, can be a good candidate for adding it to > the > >>> spec (this how it was with `Function.prototype.bind`, e.g., although > today > >>> monkey-patching is a bad practice of course). > >>> > >>> In addition, you can monkey-patch just `-1`, and other indexes, e.g. a > >>> gist from 5 years old, when a similar topic was proposed here: > >>> https://gist.github.com/DmitrySoshnikov/984921 > >>> > >>> Dmitry > >>> > >>> _______________________________________________ > >>> es-discuss mailing list > >>> [email protected] > >>> https://mail.mozilla.org/listinfo/es-discuss > >>> > >> > >> > >> > >> ---------- Forwarded message ---------- > >> From: "Alican Çubukçuoğlu" <[email protected]> > >> To: [email protected] > >> Cc: > >> Date: Fri, 22 Jan 2016 22:32:42 +0200 > >> Subject: Re: Re: Javascript Language feature Idea > >> More cool stuff: > >> ```javascript > >> const arr = [1, 2, 3]; > >> > >> // Easy push > >> arr[] = 4; // => arr[arr.length]; > >> > >> // Easy s(p)lice > >> arr[begin, end];, > >> arr[begin,]; // => arr[begin, arr.length]; > >> arr[begin, end] = [1, 2, 3]; > >> ``` > >> > >> A terrible example (terrible because this should be done with WebGL > >> shaders): > >> ```javascript > >> const image = [ /* Umbagajillion of RGBA pixels */ ]; > >> > >> function manipulate(rgba) { > >> rgba[0] += 10; > >> rgba[1] += 10; > >> rgba[2] += 10; > >> } > >> > >> for (let i = 0; i < image.length / 4; i++) { > >> const begin = i * 4; > >> const end = begin + 4; > >> > >> /* > >> In case easy s(p)lice doesn't actually Array.p.slice > >> and just creates a limited view of the array > >> without breaking reference > >> (image[begin, end] === image[begin, end]) > >> */ > >> manipulate(image[begin, end]); > >> > >> /* > >> In case easy s(p)lice does Array.p.slice > >> and creates a new array > >> (image[begin, end] !== image[begin, end]) > >> */ > >> const pixel = image[begin, end]; > >> manipulate(pixel); > >> image[begin, end] = pixel; > >> } > >> ``` > >> > >> > >> ---------- Forwarded message ---------- > >> From: kdex <[email protected]> > >> To: [email protected] > >> Cc: > >> Date: Fri, 22 Jan 2016 22:00:01 +0100 > >> Subject: Re: Javascript Language feature Idea > >> I really adore the slicing syntax. Just as a quick fix, though, > >> > arr[begin,]; // => arr[begin, arr.length]; > >> should obviously return `arr[begin, arr.length - 1]`. > >> > >> Honestly, I'm not too sure if the "easy push" syntax is particularly > self- > >> explanatory. There might be better alternatives. > >> > >> On Freitag, 22. Januar 2016 22:32:42 CET Alican Çubukçuoğlu wrote: > >> > More cool stuff: > >> > ```javascript > >> > const arr = [1, 2, 3]; > >> > > >> > // Easy push > >> > arr[] = 4; // => arr[arr.length]; > >> > > >> > // Easy s(p)lice > >> > arr[begin, end];, > >> > arr[begin,]; // => arr[begin, arr.length]; > >> > arr[begin, end] = [1, 2, 3]; > >> > ``` > >> > > >> > A terrible example (terrible because this should be done with WebGL > >> > shaders): > >> > ```javascript > >> > const image = [ /* Umbagajillion of RGBA pixels */ ]; > >> > > >> > function manipulate(rgba) { > >> > rgba[0] += 10; > >> > rgba[1] += 10; > >> > rgba[2] += 10; > >> > } > >> > > >> > for (let i = 0; i < image.length / 4; i++) { > >> > const begin = i * 4; > >> > const end = begin + 4; > >> > > >> > /* > >> > In case easy s(p)lice doesn't actually Array.p.slice > >> > and just creates a limited view of the array > >> > without breaking reference > >> > (image[begin, end] === image[begin, end]) > >> > */ > >> > manipulate(image[begin, end]); > >> > > >> > /* > >> > In case easy s(p)lice does Array.p.slice > >> > and creates a new array > >> > (image[begin, end] !== image[begin, end]) > >> > */ > >> > const pixel = image[begin, end]; > >> > manipulate(pixel); > >> > image[begin, end] = pixel; > >> > } > >> > ``` > >> > >> > >> > >> > >> > >> ---------- Forwarded message ---------- > >> From: kdex <[email protected]> > >> To: [email protected] > >> Cc: > >> Date: Fri, 22 Jan 2016 22:14:20 +0100 > >> Subject: Re: Javascript Language feature Idea > >> Standardizing unused array keys breaks compatibility about as much as > >> extending the prototype does, really. Users can already mangle with > both. > >> > >> The problems are a little more subtle, and yes, it would severely break > >> backwards compatibility. Consider this example (accessing an element > based > >> on > >> a computed index): > >> > >> ```js > >> let a = [1, 2, 3]; > >> let occurrence = a.indexOf(4); > >> a[occurrence]; > >> ``` > >> > >> Currently, this should result in `undefined`. After your proposal, you > >> could > >> introduce a potential bug into every program that accesses arrays using > an > >> index computed with `Array.prototype.indexOf`, since it would now return > >> `3`. > >> > >> On Freitag, 22. Januar 2016 18:59:06 CET Sander Deryckere wrote: > >> > Since Array inherits from Object, it can have any key, including the > key > >> > "-1". So something like list[-1] would break compatibility as users > can > >> > now > >> > already assign values to the index -1. > >> > > >> > If you want a short way to access the last element, it should probably > >> > be a > >> > function in the Array prototype. Something like list.last(). > >> > > >> > Regards, > >> > Sander > >> > > >> > 2016-01-22 18:53 GMT+01:00 RacerD123 <[email protected]>: > >> > > In other programming languages such as python, you can specify the > >> > > last > >> > > element of a list with "list[-1]" but in javascript you have to do > >> > > "list[list.length-1]". Is there maybe a way to make this feature in > >> > > javascript? > >> > > > >> > > _______________________________________________ > >> > > es-discuss mailing list > >> > > [email protected] > >> > > https://mail.mozilla.org/listinfo/es-discuss > >> > >> > >> > >> > >> > >> ---------- Forwarded message ---------- > >> From: Benoit Marchant <[email protected]> > >> To: kdex <[email protected]> > >> Cc: [email protected] > >> Date: Fri, 22 Jan 2016 13:35:55 -0800 > >> Subject: Re: Javascript Language feature Idea > >> Interesting! More pedestrian, it would be nice to finally have a version > >> of splice that doesn't create a new other Array as a side effect. > >> > >> > On Jan 22, 2016, at 13:00, kdex <[email protected]> wrote: > >> > > >> > I really adore the slicing syntax. Just as a quick fix, though, > >> >> arr[begin,]; // => arr[begin, arr.length]; > >> > should obviously return `arr[begin, arr.length - 1]`. > >> > > >> > Honestly, I'm not too sure if the "easy push" syntax is particularly > >> > self- > >> > explanatory. There might be better alternatives. > >> > > >> >> On Freitag, 22. Januar 2016 22:32:42 CET Alican Çubukçuoğlu wrote: > >> >> More cool stuff: > >> >> ```javascript > >> >> const arr = [1, 2, 3]; > >> >> > >> >> // Easy push > >> >> arr[] = 4; // => arr[arr.length]; > >> >> > >> >> // Easy s(p)lice > >> >> arr[begin, end];, > >> >> arr[begin,]; // => arr[begin, arr.length]; > >> >> arr[begin, end] = [1, 2, 3]; > >> >> ``` > >> >> > >> >> A terrible example (terrible because this should be done with WebGL > >> >> shaders): > >> >> ```javascript > >> >> const image = [ /* Umbagajillion of RGBA pixels */ ]; > >> >> > >> >> function manipulate(rgba) { > >> >> rgba[0] += 10; > >> >> rgba[1] += 10; > >> >> rgba[2] += 10; > >> >> } > >> >> > >> >> for (let i = 0; i < image.length / 4; i++) { > >> >> const begin = i * 4; > >> >> const end = begin + 4; > >> >> > >> >> /* > >> >> In case easy s(p)lice doesn't actually Array.p.slice > >> >> and just creates a limited view of the array > >> >> without breaking reference > >> >> (image[begin, end] === image[begin, end]) > >> >> */ > >> >> manipulate(image[begin, end]); > >> >> > >> >> /* > >> >> In case easy s(p)lice does Array.p.slice > >> >> and creates a new array > >> >> (image[begin, end] !== image[begin, end]) > >> >> */ > >> >> const pixel = image[begin, end]; > >> >> manipulate(pixel); > >> >> image[begin, end] = pixel; > >> >> } > >> >> ``` > >> > > >> > > >> > _______________________________________________ > >> > es-discuss mailing list > >> > [email protected] > >> > https://mail.mozilla.org/listinfo/es-discuss > >> > >> > >> _______________________________________________ > >> es-discuss mailing list > >> [email protected] > >> https://mail.mozilla.org/listinfo/es-discuss > >> > > > > > > _______________________________________________ > > es-discuss mailing list > > [email protected] > > https://mail.mozilla.org/listinfo/es-discuss > > > > > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss > >
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