Why does this anonymous function see what's under it?

Question

Why can the first anonymous function 'see' the functions under it such as foo? Shouldn't it only see what it is above it? Thanks.

window.onload = function(){
    foo();
}

function foo(){
    alert("hello");
}

Function (and variable) declarations are processed before any code is executed, also called "hoisting". — RobG, Jan 11 '17 at 23:34
@Barmar Although the same language mechanism is at play, that other question is different. — Maxim Egorushkin, Jan 12 '17 at 17:18

score 0 · Accepted Answer · answered Jan 11 '17 at 23:34

0

See function declaration hoisting:

Function declarations in JavaScript are hoisting the function definition. You can use the function before you declared it:
hoisted(); // logs "foo"

function hoisted() {
   console.log("foo");
}

answered Jan 11 '17 at 23:34

Maxim Egorushkin

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I'll blame caching in the mobile client then. – Makoto Jan 11 '17 at 23:38
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Not just *function* declarations, *variable* declarations (not the initialization value) are hoisted to the top of their enclosing scope as well. So, `var f = function(){...}` will hoist as well. Not the value (the function), but the variable (`f`). – Scott Marcus Jan 11 '17 at 23:40

score 0 · Answer 2 · edited May 23 '17 at 11:45

0

This is due to function hoisting. In JavaScript, function declarations are "hoisted" to the top of their scope, which, as you noticed, allows functions declared anywhere in the file to be called.

edited May 23 '17 at 11:45

Community

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answered Jan 11 '17 at 23:34

Peter Olson

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Not just *function* declarations, all variable declarations are hoisted to the top of their scope as well. Not the assigned values, but the declarations. – Scott Marcus Jan 11 '17 at 23:47

Why does this anonymous function see what's under it?

2 Answers2