js this是window

// 全局上下文中 this 指向 window
console.log(this === window); // true

function globalFunction() {
  console.log(this === window); // true
}
globalFunction();

const obj = {
  method: function() {
    console.log(this === obj); // true
  }
};
obj.method();

function ConstructorFunction() {
  this.value = 42;
  console.log(this); // ConstructorFunction {value: 42}
}
new ConstructorFunction();

const arrowFunction = () => {
  console.log(this === window); // true，箭头函数中的 this 继承自定义时的上下文
};
arrowFunction();

function myFunction() {
  console.log(this);
}
const boundFunction = myFunction.bind(someObject);
boundFunction(); // this 将指向 someObject

const obj = {
  method: function() {
    setTimeout(() => {
      console.log(this); // this 指向 obj
    }, 100);
  }
};
obj.method();

function myFunction() {
  console.log(this);
}
myFunction.call(someObject); // this 指向 someObject
myFunction.apply(someObject); // this 指向 someObject