What are the 5 ways to deduplicate ES6 arrays?

5 methods: 1. Use Set structure and Array.from(), syntax "Array.from(new Set(arr))"; 2. Use Set structure and expansion operator, syntax "[. ..new Set(arr)]"; 3. Traverse the array and use indexOf() to remove duplicates in the loop body.

The operating environment of this tutorial: Windows 7 system, ECMAScript version 6, Dell G3 computer.

5 ES6 array deduplication methods

1. Set data structure and Array.from() deduplication

let arr=[1,2,3,3,2,"1",0,undefined,undefined];
let newArr=Array.from(new Set(arr));
console.log(newArr);

2. Set data structure and spread operator "..." to remove duplicates

let arr=[1,2,3,3,2,"1",0,1,2];
let newArr=[...new Set(arr)];
console.log(newArr);

3. Use the single-layer loop indexOf to remove duplicates

var arr=[1,2,3,3,2,"1",0,1,2,undefined,undefined];
var newArr = [];
for(let i = 0;i <arr.length;i++){
    if(newArr.indexOf(arr[i]) ===-1) {
      newArr.push(arr[i]);
    }
}
console.log(newArr);

4. Use the includes method of the array to remove duplicates

var arr=[1,2,3,3,2,"1",0,1,2,undefined,undefined];
var newArr = [];
for(let i = 0;i <arr.length;i++){
  if(!newArr.includes(arr[i])){
    newArr.push(arr[i]);
  }
}
console.log(newArr);

5. Use the filter method of the array to remove duplicates

var arr=[1,2,3,3,2,"1",0,1,2,undefined,undefined];
var newArr = arr.filter((item,index)=> {
  return arr.indexOf(item,0) === index;
});
console.log(newArr);

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