How to add a new API to the prototype of the built-in object-take array deduplication as an example

To add a new API to the prototype of the built-in object, that is, write a new public method through the prototype, and then call the method through the object of the array.

The new API implementation method is added to the built-in object: Constructor.prototype.newFunctionName = function () {…}

		/**
		 * 	数组去重 API 
		 *  定义一个 hash数组用其下标存储 arr的元素值，以去除重复的元素
		 *  定义一个新的 result数组存储 arr去重后的元素，调用结束后作为返回值
		 */
		Array.prototype.removalDup = function(){
			var hash = [],
			    result = [];
			if(this.length){
				for(var i = 0; i < this.length;i++){
					// 判断 hash数组中的元素是否为 undefined再取反
					if(!hash[this[i]]){
						// 未重复的元素赋上任意的值(只要 Boolean值为 true即可)
						hash[this[i]] = true;
						// 将未重复的元素插入到 result数组中
						result.push(this[i]);
					}
				}	
			}
			// 返回去重后的 result数组
			return result;	
		}
		var arr = [3,2,3,3,2,4,5,2,2,6,3,8,9,3,10];
		var new_arr = arr.removalDup();

Output effect:

Array.prototype method without adding deduplication API:

Initial elements of array arr: [3,2,3,3,2,4,5,2,2,6,3,8,9,3,10]

###### The method of adding Array.prototype to the deduplication API:
Compared with the original Array prototype, it is obvious that the new Array adds an API we wrote: removalDup ();

Array arr elements after deduplication: [3, 2, 4, 5, 6, 8, 9, 10]