Why is this variable 4？

Question

console.log(window.b,b) //undefined undefined
if(true){
    console.log(b) //ƒ b(){} does it get hoisted?
    b = 4
    function b(){}
    b = 3
    console.log(b) //3  Why is this variable 3
}
console.log(window.b,b) //4 4   Why is this variable 4

If the code removes this line

function b(){}

The browser will report an error VM114:1 Uncaught ReferenceError: b is not defined at line 1 console.log(window.b,b)

Can someone tell me why it works like this？？

if function b gets hoisted, does it equals to

console.log(window.b,b) //undefined undefined why it doesn't cause an ReferenceError b is not defined
if(true){
    function b(){}
    b = 4
    b = 3
    console.log(b) // 3
}
console.log(window.b,b)  // ƒ b(){} ƒ b(){}

I am not a native English speaker,hope you can understand.

Does this answer your question? [Javascript function scoping and hoisting](https://stackoverflow.com/questions/7506844/javascript-function-scoping-and-hoisting) — Darth, Aug 14 '20 at 13:59
Check this out. https://www.w3schools.com/js/js_hoisting.asp — ismetguzelgun, Aug 14 '20 at 14:13
I was mistaken, hoisting works in both local/global (or script) scope — Zorgatone, Aug 14 '20 at 16:10
Function declarations inside `if` blocks have always been kinda wonky. [Strict mode](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode) disallows this for that reason; which I recommend you always use. — TiiJ7, Aug 14 '20 at 16:12
Also can you add information about the browser error when you remove the b function line? Can you tell us if you’re in strict mode or not? — Zorgatone, Aug 14 '20 at 16:13
@Zorgatone I updated my question. and I am not in strict mode, if I use the strict mode, two example throw the same `ReferenceError` at line 1. — lei lee, Aug 14 '20 at 16:23
@TiiJ7 ok，I just want to figure out how to explain the wonky performance，is it a Bug of JavaScript？ — lei lee, Aug 14 '20 at 16:27

score 2 · Answer 1 · answered Aug 14 '20 at 14:00

2

Because your function b gets hoisted. AS soon its reaches b = 4 a value is assigned to it.

answered Aug 14 '20 at 14:00

bill.gates

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Why is this variable 4？

1 Answers1