Using function.prototype.bind directly on function declaration

Question

Why is this allowed ?

var f = function() {
  console.log(this.x);
}.bind({x:1})();

And why this is not or better why I get syntax error in this case ?

function f() {
  console.log(this.x);
}.bind({x:1})();

So, why I need function expression syntax to get this work and is there a way to use bind method directly on function declaration ?

A function declaration is not an expression, so you can't do that. But you can force an expression `!function f(){}.bind({x:1})()`. Look for info on [IIFE](http://stackoverflow.com/questions/8228281/what-is-the-function-construct-in-javascript). — elclanrs, Apr 09 '15 at 00:20
Because it is not an expression. The syntax is ambiguous, you have to disambiguate by forcing an expression. Check the spec for more info http://www.ecma-international.org/ecma-262/5.1/#sec-13 — elclanrs, Apr 09 '15 at 00:34
Thanks, this is one more reason for throwing away function declaration and always using expression form. I can use methods directly, no hoisting... — user3448600, Apr 09 '15 at 00:39

score 4 · Answer 1 · answered Apr 09 '15 at 00:21

4

The second example works but the syntax is slightly off:

Surround the function in parens. I have to say that I'm not entirely sure why. It seems like it would work without the parens huh? :P

(function f() {
    console.log(this.x);
}).bind({x:1})();

answered Apr 09 '15 at 00:21

Halcyon

3

parens make an expression, and thus an anon function, and thus a "tail value". you can also do the prefix-only alternative to paren wraps: `0||` – dandavis Apr 09 '15 at 01:15

1 Answers1