js数组去重

1、for嵌套for循环
var arr = [1, 3, 5, 6, 5, 6, 2, 3, 4];
for(var i = 0; i <= arr.length - 1; i++) {
for(var j = i + 1; j <= arr.length; j++) {
if(arr[i] === arr[j]){
arr.splice(j, 1);
j--
}
}
};
console.log(arr);

2、sort
var arr = [1, 3, 5, 6, 5, 6, 2, 3, 4];
arr.sort();
var arr1 = [];
arr1.push(arr[0]);
for(var i = 1; i < arr.length; i++) {
if(arr[i] !== arr[i-1]) {
arr1.push(arr[i])
}
};
console.log(arr1);

3、filter
var arr = [1, 3, 5, 6, 5, 6, 2, 3, 4];
var arr1 = arr.filter((item, index, arr) => {
return arr.indexOf(item) === index
})
console.log(arr1);