问为什么这个变量是4？

EN

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

function b(){}

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(){}