Summary of array element deduplication

Summary of deduplication methods
① Traverse the empty array, indexOf method
var n = []; //A new temporary array
for(var i = 0; i < arr.length; i++){//Traverse the empty array
                                                                                                                                                                                                   ② You can also create empty objects
var n = {};
for(var i=0;i< arr.length;i++)