检查是否从Window内部调用函数的显式方法

Question

是否有比if (typeof this.value == "undefined")更明确的方法来检查是否从Window内部调用了函数 在下面的代码中？

很明显，我正在对Window进行检查，例如：if this.name === "Window"。

function get_caller() {
  if (typeof this.value == "undefined") {
    console.log('function get_caller called from window')
  }
  else {
    console.log('function get_caller called by button press')
  }
}

btn.addEventListener('click', get_caller)
get_caller()

<button id="btn">Get caller</button>

Answer 1

只需检查this是否为window：

function get_caller() {
  if (this === window) {
    console.log('function get_caller called from window')
  }
  else {
    console.log('function get_caller called by button press')
  }
}

btn.addEventListener('click', get_caller)
get_caller()

<button id="btn">Get caller</button>

Answer 2

您可以检查是否this==window或是否处于严格模式下，检查this是否为undefined，

function get_caller() {
"use strict";    // !this is used for strict mode check
 if (this == window || !this) {
    console.log('function get_caller called from window')
  }
  else {
    console.log('function get_caller called by button press')
  }
}

btn.addEventListener('click', get_caller)
get_caller()

<button id="btn">Get caller</button>