I strongly oppose. I already write a ton of code that relies on that
throwing, using that for testing purposes. I'd rather something throw
violently than to silently fail in an unexpected, potentially seemingly
unrelated place. Not even pure functional programming can act as a safety
net for implicit undefined/null access.
On Thu, Oct 29, 2015, 15:30 Ron Waldon <jokeyrh...@gmail.com> wrote:
> Has anyone considering just making dot-property access return intermediate
> undefined or null values by default?
>
> Not having to introduce new syntax would be a bonus. I'm trying to think
> of existing code that this would break and can't think of any good examples.
>
> The only compatibility issue I have thought of so far is code that relies
> on an Error being thrown but also does not check the value:
>
> ```js
> let value;
> try { value = deep.deep.deep.prop; } catch (err) { /* ... */ }
> // use value without even a basic truthy test
> ```
>
> On Fri, 30 Oct 2015, 06:07 <es-discuss-requ...@mozilla.org> wrote:
>
>
> ---------- Forwarded message ----------
> From: Laurentiu Macovei <laurentiu.maco...@gmail.com>
> To: Sander Deryckere <sander...@gmail.com>
> Cc: "es-discuss@ <es-discuss@mozilla.org>mozilla.org
> <es-discuss@mozilla.org> list" <es-discuss@mozilla.org>
> Date: Thu, 29 Oct 2015 19:52:37 +0100
> Subject: Re: Re: Existential Operator / Null Propagation Operator
>
> Yes! I have updated my answer using markdown and also posted on the
> original issue of TypeScript. https
> <https://github.com/Microsoft/TypeScript/issues/16>://
> <https://github.com/Microsoft/TypeScript/issues/16>github.com
> <https://github.com/Microsoft/TypeScript/issues/16>/Microsoft/
> <https://github.com/Microsoft/TypeScript/issues/16>TypeScript
> <https://github.com/Microsoft/TypeScript/issues/16>/issues/16
> <https://github.com/Microsoft/TypeScript/issues/16>
>
> Is there a better place to propose it for `ES6`/`ES7` ?
>
> This would be amazing operator!! Especially for `ES6`/`ES7`/`TypeScript`
>
> ```js
>
> var error = a.b.c.d; //this would fail with error if a, b or c are null or
> undefined.
>
> var current = a && a.b && a.b.c && a.b.c.d; // the current messy way to
> handle this
>
> var currentBrackets = a && a['b'] && a['b']['c'] && a['b']['c']['d'];
> //the current messy way to handle this
>
> var typeScript = a?.b?.c?.d; // The typescript way of handling the above
> mess with no errors
>
> var typeScriptBrackets = a?['b']?['c']?['d']; //The typescript of handling
> the above mess with no errors
>
> ```
>
> However I propose a more clear one - as not to confuse ? from the a ? b :
> c statements with a?.b statements:
>
> ```js
>
> var doubleDots = a..b..c..d; //this would be ideal to understand that you
> assume that if any of a, b, c is null or undefined the result will be null
> or undefined.
>
> var doubleDotsWithBrackets = a..['b']..['c']..['d'];
>
> ```
>
> For the bracket notation, I recommend two dots instead of a single one as
> it's consistent with the others when non brackets are used. Hence only the
> property name is static or dynamic via brackets.
>
> Two dots, means if its null or undefined stop processing further and
> assume the result of expression is null or undefined. (as d would be null
> or undefined).
>
> Two dots make it more clear, more visible and more space-wise so you
> understand what's going on.
>
> This is not messing with numbers too - as is not the same case e.g.
>
> ```js
>
> 1..toString(); // works returning '1'
>
> var x = {};
>
> x.1 = {y: 'test' }; //fails currently
>
> x[1] = {y: 'test' }; //works currently
>
> var current = x[1].y; //works
>
> var missing= x[2].y; //throws exception
>
> var assume= x && x[2] && x[2].y; // works but very messy
>
> ```
>
> About numbers two options: Your call which one can be adopted, but I
> recommend first one for compatibility with existing rules!
>
> 1. Should fail as it does now (`x.1.y` == `runtime error`)
>
> ```js
>
> var err = x..1..y; // should fail as well, since 1 is not a good property
> name, nor a number to call a method, since it's after x object.
>
> ```
>
> 2. Should work since it understands that is not a number calling a
> property from `Number.prototype`
>
> ```js
>
> var err = x..1..y; // should work as well, resulting 'test' in this case
>
> var err = x..2..y; // should work as well, resulting undefined in this case
>
> ```
>
> With dynamic names:
>
> ```js
>
> var correct1 = x..[1]..y; //would work returning 'test'
>
> var correct2 = x..[2]..y; //would work returning undefined;
>
> ```
>
> What do you think folks?
>
> Best Regards,
>
> Laurenţiu Macovei
>
>
> _______________________________________________
> es-discuss mailing list
> es-discuss@mozilla.org
> https://mail.mozilla.org/listinfo/es-discuss
>
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