1. […new Set(array)]去重
1.1去除数组重复成员:
let old_array = [1, 2, 3, 4, 4]
let new_array = [...new Set(old_array)]
console.log(new_array) // [1, 2, 3, 4]
1.2去除字符串里面的重复字符:
let old_str = 'ababbc'
let new_str = [...new Set(old_str)].join('')
console.log(new_str ) // "abc"
2.Array.from去重
Array.from方法可以将 Set 结构转为数组。
function dedupe(array) {
return Array.from(new Set(array));
}
console.log(dedupe([1, 1, 2, 3])) // [1, 2, 3]
3.indexOf () 方法去重
arr = ['blue', 'green', 'blue', 'yellow', 'black', 'yellow', 'blue', 'green', 'blue', 'blue', 'blue']
function unique(arr) {
var newArr = [];
for (var i = 0; i < arr.length; i++) {
if (newArr.indexOf(arr[i]) === -1) {
newArr.push(arr[i]);
}
}
return newArr
}
console.log(unique(arr)); // 输出结果: (4) ["blue", "green", "yellow", "black"]
补充
#使用 Set 实现并集、交集和差集
let a = new Set([1, 2, 3]);
let b = new Set([4, 3, 2]);
// 并集
let union = new Set([...a, ...b]);
// Set {1, 2, 3, 4}
// 交集
let intersect = new Set([...a].filter(x => b.has(x)));
// set {2, 3}
// (a 相对于 b 的)差集
let difference = new Set([...a].filter(x => !b.has(x)));
// Set {1}