How to deduplicate an array
1. Use set in ES6 to deduplicate
var arr = [1, 8, 5, 3, 1, 5, 2, 6];
function only(arr) {
return Array.from(new Set(arr));
}
console.log(only(arr));
display effect:
2, set and destructuring assignment to remove duplication
var arr = [1, 8, 5, 3, 1, 5, 2, 6];
function only(arr) {
return [...new Set(arr)];
}
console.log(only(arr));
display effect:
3. Use double for loops, combined with splice to remove duplicates:
var arr = [1, 8, 5, 3, 1, 5, 2, 6];
function only(arr) {
let i, j;
for (i = 0; i < arr.length; i++) {
for (j = i + 1; j < arr.length; j++) {
if (arr[i] == arr[j]) {
arr.splice(j, 1);
j--;
}
}
}
return arr;
}
console.log(only(arr));
display effect:
4. Use indexOf for array deduplication
var arr = [1, 8, 5, 3, 1, 5, 2, 6];
function only(arr) {
let i, newArr = [];
for (i = 0; i < arr.length; i++) {
if (newArr.indexOf(arr[i]) == -1) {
newArr.push(arr[i]);
}
}
return newArr
}
console.log(only(arr));
display effect:
5. Use object key-value pairs for deduplication
var arr = [1, 8, 5, 3, 1, 5, 2, 6];
function only(arr) {
let i, newArr = [], obj = {
};
for (i = 0; i < arr.length; i++) {
if (!obj[arr[i]]) {
newArr.push(arr[i]);
obj[arr[i]] = 1;
}
}
return newArr
}
console.log(only(arr));
display effect: