js数组操作方法总结(必看篇)

来源：一二三四网

判断数值数组中各个数字出现的奇偶次数

<!DOCTYPE html> 
<html> 
 <head> 
 <meta charset="utf-8"> 
 <title>数组操作</title> 
 </head> 
 <body> 
 <script type="text/javascript"> 
 var arr=[3,1,2,2,1,3,1]; 
 var sum=[]; 
 var res=[]; 
 var count=0; 
 var temp; 
 for(var i=0;i<arr.length;i++){ 
 if(res.indexOf(arr[i])==-1){ 
 res.push(arr[i]); 
 } 
 } 
 for(var i=0;i<res.length;i++){ 
 for(var j=0;j<arr.length;j++){ 
 if(arr[j]==res[i]){ 
 count++; 
 } 
 } 
 sum.push(count); 
 count=0; 
 } 
 console.log(res);//[3,1,2] 
 for(var i=0;i<res.length;i++){ 
 var str=(sum[i]%2==0)?"偶数":"奇数"; 
 console.log(res[i]+"出现了"+sum[i]+"次"); 
 console.log(res[i]+"出现了"+str+"次"); 
 } 
 </script> 
 </body> 
</html>

阿里笔试-数组操作-找出两个数组中不同的元素

<script type="text/javascript"> 
 function diff(arr1,arr2){ 
 var ress = []; 
 var arr = arr1.concat(arr2); 
 for(var i=0,len=arr.length;i<len;i++){ 
 if((arr1.indexOf(arr[i])>=0 && arr2.indexOf(arr[i])<0) || (arr1.indexOf(arr[i])<0 && arr2.indexOf(arr[i])>=0)){ 
 ress.push(arr[i]); 
 } 
 } 
 return ress; 
} 
var arr1 = [1,2,3,5,7,6]; 
var arr2 = [1,2,5]; 
var res = diff(arr1,arr2); 
console.log(res);//[3, 7, 6] 
</script>

数组去重

方法1

<!DOCTYPE html> 
<html> 
 <head> 
 <meta charset="utf-8"> 
 <title>数组去重01</title> 
 </head> 
 <body> 
 <script type="text/javascript"> 
 //给数组原型添加方法 
 Array.prototype.unique = function(){ 
 var arr = []; 
 for(var i=0,i=this.length;i<len;i++){ 
 if(arr.indexOf(this[i]) == -1){ 
 arr.push(this[i]); 
 } 
 } 
 return arr; 
 }; 
 console.log([1,2,3,2,5,6,3].unique());//[1, 2, 3, 5, 6] 
 </script> 
 </body> 
</html>

方法2

<!DOCTYPE html> 
<html> 
 <head> 
 <meta charset="utf-8"> 
 <title>数组去重02</title> 
 </head> 
 <body> 
 <script type="text/javascript"> 
 Array.prototype.unique = function(){ 
 var n = {}, 
 r=[]; //n为哈希表，r为临时数组 
 for(var i = 0; i < this.length; i++) //遍历当前数组 
 { 
 if (!n[this[i]]) //如果hash表中没有当前项 
 { 
 n[this[i]] = true; //存入哈希表 
 r.push(this[i]); //把当前数组的当前项push到临时数组里面 
 } 
 } 
 return r; 
 } 
 console.log([1,2,3,2,5,6,3].unique());//[1, 2, 3, 5, 6] 
 </script> 
 </body> 
</html>

方法3

<!DOCTYPE html> 
<html> 
 <head> 
 <meta charset="utf-8"> 
 <title>数组去重</title> 
 </head> 
 <body> 
 <script type="text/javascript"> 
 Array.prototype.unique = function(){ 
 var arr = [this[0]];//结果数组 
 for(var i=1;i<this.length;i++){//从第二项开始遍历 
 if(this.indexOf(this[i]) == i){ 
 //如果当前数组的第i项在当前数组中第一次出现的位置不是i，那么表示第i项是重复的，忽略掉。否则存入结果数组 
 arr.push(this[i]); 
 } 
 } 
 return arr; 
 } 
 console.log([1,2,3,4,2,3,4].unique());// [1, 2, 3, 4] 
 </script> 
 </body> 
</html>

方法4

<!DOCTYPE html> 
<html> 
<head> 
 <meta charset="utf-8"> 
 <meta http-equiv="X-UA-Compatible" content="IE=edge"> 
 <title>filter</title> 
 <link rel="stylesheet" href=""> 
</head> 
<body> 
<script type="text/javascript"> 
var arr = [4,5,3,2,3,4,5,1]; 
function fn(num){ 
 var res = num.filter(function(item,index,array){ 
 return num.indexOf(item) === index;//num.indexOf(item)将会返回元素在数组第一次出现的位置 
 //对于多次出现的元素，除第一次外，其他情况都返回false 
 }); 
 return res; 
} 
console.log(fn(arr));//[4, 5, 3, 2, 1] 
</script> 
</body> 
</html>

方法5

<!DOCTYPE html> 
<html> 
<head> 
 <meta charset="utf-8"> 
 <meta http-equiv="X-UA-Compatible" content="IE=edge"> 
 <title>Object 对象来当做哈希表</title> 
 <link rel="stylesheet" href=""> 
</head> 
<body> 
<script type="text/javascript"> 
function unique(a) { 
 var obj = {}; 
 return a.filter(function(item) {//filter会返回true的项组成的成员 
 return obj.hasOwnProperty(item) ? false : (obj[item] = true); 
 }); 
} 
 
var a = [1, 1, 3, 2, 1, 2, 4]; 
var res = unique(a); 
console.log(res); // [1, 3, 2, 4] 
</script> 
</body> 
</html>