Home > Article > Web Front-end > Summary of several methods to achieve array deduplication in js
Double-layer loop, outer loop element, compare value when inner loop
If there is the same value If it is different, it will be pushed into the array.
Array.prototype.distinct = function(){var arr = this, result = [], i, j, len = arr.length;for(i = 0; i < len; i++){for(j = i + 1; j < len; j++){if(arr[i] === arr[j]){ j = ++i; } } result.push(arr[i]); }return result; }var arra = [1,2,3,4,4,1,1,2,1,1,1]; arra.distinct(); //返回[3,4,2,1]
Double-layer loop, outer loop element, compare value when inner loop
If the value is the same, delete this value
Notes
: After deleting elements, you need to reduce the length of the array by 1.
Array.prototype.distinct = function (){var arr = this, 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; };var a = [1,2,3,4,5,6,5,3,2,4,56,4,1,2,1,1,1,1,1,1,];var b = a.distinct(); console.log(b.toString()); //1,2,3,4,5,6,56
Advantages: Simple and easy to understand
Disadvantages: High memory usage and slow speed
Array.prototype.distinct = function (){var arr = this, i, obj = {}, result = [], len = arr.length;for(i = 0; i< arr.length; i++){if(!obj[arr[i]]){ //如果能查找到,证明数组元素重复了obj[arr[i]] = 1; result.push(arr[i]); } }return result; };var a = [1,2,3,4,5,6,5,3,2,4,56,4,1,2,1,1,1,1,1,1,];var b = a.distinct(); console.log(b.toString()); //1,2,3,4,5,6,56
Use recursive thinking
Sort first, then compare from the end, if they are the same, delete
Array.prototype.distinct = function (){var arr = this, len = arr.length; arr.sort(function(a,b){ //对数组进行排序才能方便比较return a - b; })function loop(index){if(index >= 1){if(arr[index] === arr[index-1]){ arr.splice(index,1); } loop(index - 1); //递归loop函数进行去重 } } loop(len-1);return arr; };var a = [1,2,3,4,5,6,5,3,2,4,56,4,1,2,1,1,1,1,1,1,56,45,56];var b = a.distinct(); console.log(b.toString()); //1,2,3,4,5,6,45,56
indexOf
and forEach
Array.prototype.distinct = function (){var arr = this, result = [], len = arr.length; arr.forEach(function(v, i ,arr){ //这里利用map,filter方法也可以实现var bool = arr.indexOf(v,i+1); //从传入参数的下一个索引值开始寻找是否存在重复if(bool === -1){ result.push(v); } })return result; };var a = [1,1,1,1,1,1,1,1,1,2,2,2,2,2,2,3,3,3,3,3,3,3,2,3,3,2,2,1,23,1,23,2,3,2,3,2,3];var b = a.distinct(); console.log(b.toString()); //1,23,2,3
Set data structure is similar to an array, and the values of its members are all unique.
Use Array.from to convert the Set structure into an array
function dedupe(array){return Array.from(new Set(array)); } dedupe([1,1,2,3]) //[1,2,3]
The expansion operator (...) uses for internally. ..of loop
let arr = [1,2,3,3]; let resultarr = [...new Set(arr)]; console.log(resultarr); //[1,2,3]
The above is the detailed content of Summary of several methods to achieve array deduplication in js. For more information, please follow other related articles on the PHP Chinese website!