1，常规双循环去重（缺点：循环次数较多）

Array.prototype.unique1 = function(){if(this === null){throw new TypeError('"this" is null or not defined');}let that = Object(this),len = that.length >>> 0;let res = [that[0]];for(let i = 1; i < len; i++){let falg = false;for(let j = 0; j < res.length; j++){if(that[i] === res[j]){falg = true;break;}}if(!falg){res.push(this[i]);}}return res;
}

注意：

（1，必须在第二个循环外push到新的数组

（2，减少循环次数，在第二个循环中找到相等值，马上退出该循环

（3，每次循环对falg检验

（4，由于第一值直接赋值，所以不用检测第一个值

2，数组的sort先排序再去重（缺点：返回数组为排序后的顺序）

Array.prototype.unique2 = function(){if(this === null){throw new TypeError('"this" is null or not defined');}let that = Object(this).sort(),len = that.length >>> 0,res = [that[0]];for(let i = 1; i < len; i++){if(that[i] !== res[res.length - 1]){res.push(that[i]);}}return res;
}

3，对象键值不重复（缺点：占内存）

Array.prototype.unique3 = function(){if(this === null){throw new TypeError('"this" is null or not defined');}let that = Object(this),len = that.length >>> 0,obj = {},res = [];for(let i = 0; i < len; i++){let type = typeof that[i];if(!obj[that[i]]){res.push(that[i]);obj[that[i]] = [type];}else if(obj[that[i]].indexOf(type) === -1){res.push(that[i]);obj[that[i]].push(type);}}return res;
}

4，indexOf检测新数组（优点：简单）

Array.prototype.unique4 = function(){if(this === null){throw new TypeError('"this" is null or not defined');}let that = Object(this),len = that.length >>> 0,res = [that[0]];for(let i = 1; i < len; i++){if(res.indexOf(that[i]) === -1){res.push(that[i]);}}return res;
}

5，indexOf检测原数组

Array.prototype.unique5 = function(){if(this === null){throw new TypeError('"this" is null or not defined');}let that = Object(this),len = that.length >>> 0,res = [that[0]];for(let i = 1; i < len; i++){if(that.indexOf(that[i]) === i){res.push(that[i]);}}return res;
}

6，数组的every方法

Array.prototype.unique6 = function(){if(this === null){throw new TypeError('"this" is null or not defined');}let that = Object(this),len = that.length >>> 0,res = [that[0]];for(let i = 1; i < len; i++){if(res.every(function(val){return val !== that[i]})){res.push(that[i]);}}return res;
}

注意：如果发现了一个这样的元素，every 方法将会立即返回 false。否则，callback 为每一个元素返回 true，every 就会返回 true。

7，数组的some方法

Array.prototype.unique10 = function(){if(this === null){throw new TypeError('"this" is null or not defined');}let that = Object(this),len = that.length >>> 0,res = [that[0]];for(let i = 1; i < len; i++){if(!res.some(function(val){return val === that[i]})){res.push(that[i]);}}return res;
}

注意：如果找到了这样一个值，some 将会立即返回 true。否则，some 返回 false。
8，数组的includes方法

Array.prototype.unique7 = function(){if(this === null){throw new TypeError('"this" is null or not defined');}let that = Object(this),len = that.length >>> 0,res = [that[0]];for(let i = 1; i < len; i++){if(!res.includes(that[i])){res.push(that[i]);}}return res;
}

9，数组的filter方法

Array.prototype.unique8 = function(){if(this === null){throw new TypeError('"this" is null or not defined');}let that = Object(this),len = that.length >>> 0,res = [that[0]];for(let i = 1; i < len; i++){if(res.filter(function(val){return val === that[i]}).length === 0){res.push(that[i]);}}return res;
}

10，数组的find方法（缺点：没有做0或者false这个一类判断）

Array.prototype.unique9 = function(){if(this === null){throw new TypeError('"this" is null or not defined');}let that = Object(this),len = that.length >>> 0,res = [that[0]];for(let i = 1; i < len; i++){if(!res.find(function(val){return val === that[i]})){res.push(that[i]);}}return res;
}

还有lastIndexOf,findIndex等方法也能做去重，就不一一列举，有兴趣的可以自己做一下。

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