Add spread operator!

[Kreijstal]

Usually "apply" is used as a spread operator, here's an example
convert this

Array.prototype.concat.apply([1,2,3],[3,4,5])

into

[1,2,3].concat(...[3,4,5])

[nene]

This should be an addition to the arg-spread transform. The following works:

myArr.concat.apply(myArr, [1, 2, 3]);
// -->
myArr.concat(...[1, 2, 3]);

but the following does not:

Array.prototype.concat.apply(myArr, [1, 2, 3])

[Kreijstal]

I suppose [].concat.apply(myArr,[1,2,3]) won't work either?

[nene]

Yeah, that too.

There is a problem though, which we need to watch out for. Sometimes apply() is used to convert array-like objects to arrays:

function foo() {
  // arguments variable
  Array.prototype.slice.apply(arguments, []);
}

// NodeList
var divs = document.getElementsByTagName("div");
Array.prototype.slice.apply(divs, []);

I'm not sure how common such cases are, as one can often just use .call() instead of .apply() and one might not even need the second argument.

However, the mere possibility of these cases would render the arg-spread transform unsafe. The arguments case we can mostly account for, but the NodeList case is not really possible to detect.