一、前言:

我们在实际工作中,或者在面试找工作时,都会用到或者被问到一个问题,那就是“数组如何去重”。是的,这个问题有很多种解决方案,看看下面的十种方式吧!

二、数组去重方式大汇总:

Methods 1: 思路:定义一个新数组,并存放原数组的第一个元素,然后将元素组一一和新数组的元素对比,若不同则存放在新数组中。

functionunique(arr){varres=[arr[0]];for(vari=1;i<arr.length;i++){varrepeat=false;for(varj=0;j<res.length;j++){if(arr[i]===res[j]){repeat=true;break;}}if(!repeat){res.push(arr[i]);}}returnres;}console.log('------------方法一---------------');console.log(unique([1,1,2,3,5,3,1,5,6,7,4]));

Methods 2: 思路:先将原数组排序,在与相邻的进行比较,如果不同则存入新数组。

functionunique2(arr){vararr2=arr.sort();varres=[arr2[0]];for(vari=1;i<arr2.length;i++){if(arr2[i]!==res[res.length-1]){res.push(arr2[i]);}}returnres;}console.log('------------方法二---------------');console.log(unique2([1,1,2,3,5,3,1,5,6,7,4]));

Methods 3: 利用对象属性存在的特性,如果没有该属性则存入新数组。

functionunique3(arr){varres=[];varobj={};for(vari=0;i<arr.length;i++){if(!obj[arr[i]]){obj[arr[i]]=1;res.push(arr[i]);}}returnres;}console.log('------------方法三---------------');console.log(unique3([1,1,2,3,5,3,1,5,6,7,4]));

Methods 4: 利用数组的indexOf下标属性来查询。

functionunique4(arr){varres=[];for(vari=0;i<arr.length;i++){if(res.indexOf(arr[i])==-1){res.push(arr[i]);}}returnres;}console.log('------------方法四---------------');console.log(unique4([1,1,2,3,5,3,1,5,6,7,4]));

Methods 5: 利用数组原型对象上的includes方法。

functionunique5(arr){varres=[];for(vari=0;i<arr.length;i++){if(!res.includes(arr[i])){//如果res新数组包含当前循环itemres.push(arr[i]);}}returnres;}console.log('------------方法五---------------');console.log(unique5([1,1,2,3,5,3,1,5,6,7,4]));

Methods 6: 利用数组原型对象上的 filter 和 includes方法。

functionunique6(arr){varres=[];res=arr.filter(function(item){returnres.includes(item)?'':res.push(item);});returnres;}console.log('------------方法六---------------');console.log(unique6([1,1,2,3,5,3,1,5,6,7,4]));

Methods 7: 利用数组原型对象上的 forEach 和 includes方法。

functionunique7(arr){varres=[];arr.forEach(function(item){res.includes(item)?'':res.push(item);});returnres;}console.log('------------方法七---------------');console.log(unique7([1,1,2,3,5,3,1,5,6,7,4]));

Methods 8: 利用数组原型对象上的 splice 方法。

functionunique8(arr){vari,j,len=arr.length;for(i=0;i<len;i++){for(j=i+1;j<len;j++){if(arr[i]==arr[j]){arr.splice(j,1);len--;j--;}}}returnarr;}console.log('------------方法八---------------');console.log(unique8([1,1,2,3,5,3,1,5,6,7,4]));

Methods 9: 利用数组原型对象上的 lastIndexOf 方法。

functionunique9(arr){varres=[];for(vari=0;i<arr.length;i++){res.lastIndexOf(arr[i])!==-1?'':res.push(arr[i]);}returnres;}console.log('------------方法九---------------');console.log(unique9([1,1,2,3,5,3,1,5,6,7,4]));

Methods 10: 利用 ES6的set 方法。

functionunique10(arr){//Set数据结构,它类似于数组,其成员的值都是唯一的returnArray.from(newSet(arr));//利用Array.from将Set结构转换成数组}console.log('------------方法十---------------');console.log(unique10([1,1,2,3,5,3,1,5,6,7,4]));

三、其他:

有意思的是,当我把数组的长度变得很大的时候(如下所示),测试了一下不同方法的执行时间长短,会发现方法三、四、五、六、七相对来说会更有优势,而方法八的执行速度似乎一直垫底。你也可以在你本地跑一下试试!

//测试用的超大数组
var arr = 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//这里只是举例方法三(如果你把所有方法放在一起测试,会更直观的看到执行时间的差异)

vartime3=newDate().getTime();functionunique3(arr){varres=[];varobj={};for(vari=0;i<arr.length;i++){if(!obj[arr[i]]){obj[arr[i]]=1;res.push(arr[i]);}}returnres;}console.log('------------方法三---------------');console.log(unique3(arr));console.log('3所花时间:'+(newDate().getTime()-time3));