javascript - 绑定(bind)范围 javascript

Question

我正在尝试找出使用绑定(bind)的范围。我对 boundF1 的输出感到困惑。这是怎么回事？

// console.log(x) ReferenceError: x is not defined

// setting this.x - this here is global or window
this.x = 5;
console.log(x) // 5

function f1() {
  console.log(x); // 5
  console.log(this.x); // 5
}

// Lexically bound this to window 
f2 = () => {
  console.log(x); // 5
  console.log(this.x); // 5
}

f1()
f2()

boundF1 = f1.bind({x:1});
boundF2 = f2.bind({x:1});


boundF1() // 5 1 Why is this not 1, 1. How is x resolved here? Does it check local vars, then global vars. Would it ever use this? What is the scoping rule?

boundF2() // 5 5

Answer 1

因为x将始终在范围内查找变量。它与this(上下文)无关。当您调用 .bind 时，您只需在函数内部设置 this 的值。