JavaScript 数组去重方法汇总

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        <title>JavaScript 数组去重 面试题</title>
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    <body>
        <script type="text/javascript">
            var arr = [1, 2, 3, 4, 1, 2, 5];
            //方法一：ES6 set
            var newArr = [...(new Set(arr))];
            console.log(newArr);
            //方法二：
            function dicArr(arr) {
                var newArr = [];
                for(var i = 0, len = arr.length; i < len; i++) {
                    if(newArr.indexOf(arr[i]) == -1) {
                        newArr.push(arr[i]);
                    }
                }
                return newArr;
            }
            console.log(dicArr(arr));
            //方法三
            function dicArr2(arr) {
                var newArr = [],
                    obj = {};
                for(var i = 0, len = arr.length; i < len; i++) {
                    if(!obj[arr[i]]) {
                        obj[arr[i]] = 1;
                        newArr.push(arr[i]);
                    }
                }
                return newArr;
            }
            console.log(dicArr2(arr));
            //方法四
            function dicArr3(arr) {
                for(var i = 0, len = arr.length; i < len; i++) {
                    for(var j = i + 1; j < len; j++) {
                        if(arr[i] == arr[j]) {
                            arr.splice(j, 1);
                            len--;
                            j--;
                        }
                    }
                }
                return arr;
            }
            console.log(dicArr3(arr));
            //方法五 说明使用map，filter，forEach都行
            function dicArr4(arr) {
                var newArr = [];
                //              arr.forEach(function(value,key,arr){
                //                  var flag = arr.indexOf(value,key+1);
                //                  if(flag == -1){
                //                      newArr.push(value);
                //                  }
                //              });
                //              arr.map(function(value, key, arr) {
                //                  var flag = arr.indexOf(value, key + 1);
                //                  if(flag == -1) {
                //                      newArr.push(value);
                //                  }
                //              });
                arr.filter(function(value, key, arr) {
                    var flag = arr.indexOf(value, key + 1);
                    if(flag == -1) {
                        newArr.push(value);
                    }
                });
                return newArr;
            }
            console.log(dicArr4(arr));
        </script>
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上述一共实现五种数组去重方法。
JavaScript 数组去重 方法汇总

JavaScript 数组去重方法汇总
