數組去重的幾種方法

//第一種
var arr = [1,23,1,2,23,2,3,4,3,2,5,5],newArr = [];

for (var i = 0; i <= arr.length; i++) {
if(newArr.indexOf(arr[i]) == -1){      //判斷在s數組中是否存在，不存在則push到s數組中
newArr.push(arr[i]); 
}

}

console.log(newArr);

//第二種 es6
var arr = ['1','1','23','234','33','44','22','33'];
console.log(new Set(arr));

//第三種es6數組filter()過濾
var arr = [1, 2, 2, 3, 4, 5, 5, 6, 7, 7];
var arr2 = arr.filter((x, index,self) =>self.indexOf(x)===index); 
console.log(arr2);