var d = [];
console.log(typeof d); // weird!
console.log(d.toString()); //Prints nothing since there are no elements in the array
console.log(Object.prototype.toString.call(d)); // better!
 
 当我在第一个console.log打印对象上面运行代码时，由于数组是一个对象，第二个console.log打印[object Array]，所以这是期望的。 我对Object.prototype.toString.call(d)如何工作有点困惑。 
 
 所以我知道数组原型上的toString方法只是试图打印出数组内部的元素。 但是当你在基础对象的原型上调用toString方法时，toString方法到底做了什么？ 它是否也尝试打印出数组的元素？ 基础Object上的toString方法也使用关键字this因为我们使用.call ，它会在调用函数时更改this关键字指向的内容。 

var d = [];
console.log(typeof d); // weird!
console.log(d.toString()); //Prints nothing since there are no elements in the array
console.log(Object.prototype.toString.call(d)); // better!
 
When I ran the code above the first console.log prints object, which is expected since an array is an object and the second console.log prints [object Array]. I am a little confused on how Object.prototype.toString.call(d) works.
 
So I know the toString method on the array prototype simply tries to print out the elements inside of an array. But when you call the toString method on the base Object's prototype what exactly does that toString method do? Does it try to print out the elements of the array as well? Also does the toString method on the base Object use the keyword this since we are using .call which changes what the this keyword points when a function is invoked.

原文：https://stackoverflow.com/questions/33769155