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Efficiency testing of several methods to remove duplicates from JavaScript arrays

高洛峰
高洛峰Original
2016-12-09 13:02:451284browse

The following is my summary and efficiency test of three high-efficiency methods on the Internet. If you have better opinions or suggestions, you can also put them forward and let us learn together.

Array deduplication method 1:

Array.prototype.unique1 = function(){
 console.time("数组去重法1");   //记录开始执行的时间
 var arr = [];    //创建一个临时数组
 var obj = {};   //创建一个空对象
 for(var i = 0; i < this.length; i++){   //遍历当前要去重的数组
  if(!obj[this[i]]){   //判断obj对象中是否存有当前项,没有则执行
   arr.push(this[i]);   //将当前项push到临时数组中
   obj[this[i]] = 1;   //将当前项存入obj对象
  }
 }
 console.timeEnd("数组去重法1");   //记录结束执行的时间
 return arr;
}


Array deduplication method 2:

Array.prototype.unique2 = function(){
 console.time("数组去重法2"); //记录开始执行的时间
 var arr = [];  //创建一个临时数组
 for(var i = 0; i < this.length; i++){  //遍历当前要去重的数组
  if(arr.indexOf(this[i]) == -1){  //判断临时数组中是否存有当前项,没有则执行
   arr.push(this[i]); //将当前项push到临时数组中
  }
 }
 console.timeEnd("数组去重法2"); //记录结束执行的时间
 return arr;
}


Array deduplication method 3:

Array.prototype.unique3 = function(){
 console.time("数组去重法3"); //记录开始执行的时间
 var arr = [this[0]]; //创建一个临时数组,并将要去重数组的第一项存入临时数组
 for(var i = 1; i < this.length; i++) { //从要去重数组第二项开始遍历
  if (this.indexOf(this[i]) == i){ //判断临时数组中是否存有当前项,没有则执行
   arr.push(this[i]); //将当前项push到临时数组中
  }
 }
 console.timeEnd("数组去重法3"); //记录结束执行的时间
 return arr;
}


Efficiency test method:

var arr1 = []; //创建一个要去重的数组
for(var i = 0; i < 200000; i++){ //遍历200000个数据
 arr1.push(parseInt(Math.random() * 10) + 1); //将所有数据返回为随机数(1-10之间)的数, 并push到要去重的数组中
}
 
console.log(arr1.unique1()); //打印数组去重法1的执行时间
console.log(arr1.unique2()); //打印数组去重法2的执行时间
console.log(arr1.unique3()); //打印数组去重法3的执行时间


Efficiency test results:

Efficiency testing of several methods to remove duplicates from JavaScript arrays

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