Binding to a different variable name in js is how the cljs compiler
emulates symbol-to-value binding using javascript vars.
It is equivalent to this es6 javascript using let:
{let a = 123, func = function() {return a;}; { let a = 456; }}
On Wednesday, March 13, 2019 at 12:26:15 AM UTC-5, [email protected] wrote:
>
> When I run the following CLJS code:
>
> (let [a 123
> func (fn [] a)
> a 456]
> (func))
>
> the block returns 123, which I'm absolutely fine with and have gotten used
> to since starting programming Clojure(Script).
>
> However, in JS if I run the following almost but not quite equivalent code:
>
> var a = 123,
> func = function() {return a;},
> a = 456;
>
> I of course get 456, which is also expected.
>
> So it appears, at least on the surface, that when func is created that it
> evaluates the symbol a at the time of creation, such that func actually
> becomes (fn [] 123). However, looking at the compiled JS code, what is
> actually happening is:
>
> var a_32455 = (123);
> var func_32456 = ((function (a_32455) {
> return (function () {
> return a_32455;
> });}) (a_32455) );
> var a_32457__$1 = (456);
> func_32456.call(null);
>
>
> which is fascinating, because it isn't actually what I intuitively
> expected was happening. Instead, it appears as if each instance of the
> symbol a as a binding in the let binding vector is converted to a different
> variable in the compiled JS code. So the first a becomes a_32455, and the
> second becomes a_32457__$1.
>
> This isn't actually causing me a problem at all, but I'm really interested
> to know what exactly is going on, if anyone can explain it. I also wonder
> if it is something which may trip newcomers from JavaScript and if an
> explanation should be provided somewhere?
>
> Thanks,
> Ali
>
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