JavaScript中數組去重的示例分析

這篇文章主要為大家展示了“JavaScript中數組去重的示例分析”，內容簡而易懂，條理清晰，希望能夠幫助大家解決疑惑，下面讓小編帶領大家一起研究并學習一下“JavaScript中數組去重的示例分析”這篇文章吧。

一、前言：

我們在實際工作中，或者在面試找工作時，都會用到或者被問到一個問題，那就是“數組如何去重”。是的，這個問題有很多種解決方案，看看下面的十種方式吧！

二、數組去重方式大匯總：

Methods 1: 思路：定義一個新數組，并存放原數組的第一個元素，然后將元素組一一和新數組的元素對比，若不同則存放在新數組中。

function unique(arr){
 var res = [arr[0]];
 for(var i=1; i<arr.length; i++){
  var repeat = false;
  for(var j=0; j<res.length; j++){
   if(arr[i] === res[j]){
    repeat = true;
    break;
   }
  }
  if(!repeat){
   res.push(arr[i]);
  }
 }
 return res;
}
console.log('------------方法一---------------');

console.log(unique([1,1,2,3,5,3,1,5,6,7,4]));

Methods 2: 思路：先將原數組排序，在與相鄰的進行比較，如果不同則存入新數組。

function unique2(arr){
 var arr2 = arr.sort();
 var res = [arr2[0]];
 for(var i=1; i<arr2.length; i++){
  if(arr2[i] !== res[res.length-1]){
   res.push(arr2[i]);
  }
 } 
 return res;
}

console.log('------------方法二---------------');

console.log(unique2([1,1,2,3,5,3,1,5,6,7,4]));

Methods 3: 利用對象屬性存在的特性，如果沒有該屬性則存入新數組。

function unique3(arr){
 var res = [];
 var obj = {};
 for(var i=0; i<arr.length; i++){
  if( !obj[arr[i]] ){
   obj[arr[i]] = 1;
   res.push(arr[i]);
  }
 } 
 return res;
}

console.log('------------方法三---------------');

console.log(unique3([1,1,2,3,5,3,1,5,6,7,4]));

Methods 4: 利用數組的indexOf下標屬性來查詢。

function unique4(arr){
 var res = [];
 for(var i=0; i<arr.length; i++){
  if(res.indexOf(arr[i]) == -1){
   res.push(arr[i]);
  }
 }
 return res;
}

console.log('------------方法四---------------');

console.log(unique4([1,1,2,3,5,3,1,5,6,7,4]));

Methods 5: 利用數組原型對象上的includes方法。

function unique5(arr){
 var res = [];
 
 for(var i=0; i<arr.length; i++){
  if( !res.includes(arr[i]) ){ // 如果res新數組包含當前循環item
   res.push(arr[i]);
  }
 }
 return res;
}

console.log('------------方法五---------------');

console.log(unique5([1,1,2,3,5,3,1,5,6,7,4]));

Methods 6: 利用數組原型對象上的 filter 和 includes方法。

function unique6(arr){
 var res = [];
 
 res = arr.filter(function(item){
  return res.includes(item) ? '' : res.push(item);
 });
 return res;
}

console.log('------------方法六---------------');

console.log(unique6([1,1,2,3,5,3,1,5,6,7,4]));

Methods 7: 利用數組原型對象上的 forEach 和 includes方法。

function unique7(arr){
 var res = [];
 
 arr.forEach(function(item){
  res.includes(item) ? '' : res.push(item);
 }); 
 return res;
}

console.log('------------方法七---------------');

console.log(unique7([1,1,2,3,5,3,1,5,6,7,4]));

Methods 8: 利用數組原型對象上的 splice 方法。

function unique8(arr){
 var i,
  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--;
   }
  }
 }
 return arr;
}

console.log('------------方法八---------------');

console.log(unique8([1,1,2,3,5,3,1,5,6,7,4]));

Methods 9: 利用數組原型對象上的 lastIndexOf 方法。

function unique9(arr){
 var res = []; 
 for(var i=0; i<arr.length; i++){
  res.lastIndexOf(arr[i]) !== -1 ? '' : res.push(arr[i]);
 }
 return res;
}

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。

function unique10(arr){
 //Set數據結構，它類似于數組，其成員的值都是唯一的
 return Array.from(new Set(arr)); // 利用Array.from將Set結構轉換成數組
}

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，當我把數組的長度變得很大的時候（如下所示），測試了一下不同方法的執行時間長短，會發現方法三、四、五、六、七相對來說會更有優勢，而方法八的執行速度似乎一直墊底。你也可以在你本地跑一下試試！

//測試用的超大數組
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,3,5,3,1,5,6,7,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,1,1,2,3,5,3,1,5,6,7,4,1,1,2,3,5,3,1,5,6,7,4,1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//這里只是舉例方法三（如果你把所有方法放在一起測試，會更直觀的看到執行時間的差異）

var time3 = new Date().getTime();
function unique3(arr){
 var res = [];
 var obj = {};
 for(var i=0; i<arr.length; i++){
  if( !obj[arr[i]] ){
   obj[arr[i]] = 1;
   res.push(arr[i]);
  }
 } 
 return res;
}

console.log('------------方法三---------------');

console.log( unique3(arr) );

console.log('3所花時間： ' + (new Date().getTime() - time3));

以上是“JavaScript中數組去重的示例分析”這篇文章的所有內容，感謝各位的閱讀！相信大家都有了一定的了解，希望分享的內容對大家有所幫助，如果還想學習更多知識，歡迎關注億速云行業資訊頻道！