原型函数污染JavaScript数组

Question

I'm working with an API that can accept multiple arrays in which I'm using apply() to pass the arrays, but the array contains a prototype function that I cannot seem to remove from the individual array. What ends up happening is that prototype function being executed.

This is the prototype function: if ( !Array.prototype.last ) { Array.prototype.last = function(){ return this[this.length - 1]; }} if ( !Array.prototype.last ) { Array.prototype.last = function(){ return this[this.length - 1]; }}

For example when I log each array I see the following in my eventList array:

["name1", "index1", "value1", last: function]
["name2", "index2", "value2", last: function]
["name3", "index3", "value3", last: function]

I then push the arrays:

apiName.push.apply( apiName, eventList );

I've tried array.pop() to remove the 'last' function on each array, but to no avail.

How does the prototype function end up in the array in the first place and how would I prevent it from being called in the apply()?

Thanks for any insight!

Answer 1

Arrays are Objects in JavaScript. They can have properties and prototypes just like an Object.

Ex:

var a = [];
a.foo = "bar";

This is completely valid. But is "bar" in the Array ?

Let's ask:

console.log(a.length); // 0
console.log(a.foo); // "bar"

So: no , it's not in the Array but it does exist as a property of the Object.

Just like with properties adding things to the prototype doesn't affect the value of .length .

It's a bit unfortunate (confusing) that you see the custom prototype when logging, but I would attribute that to a customization in your debugger.