js:多种方法实现数组去重

var arr = [1, 4, 2, 1, 5, 4, 2, 5, 6, ‘2‘, 3, 1]
//自己重复判断（删除/添加）
var a = [...arr]
for (var i = a.length - 1; i > 0; i--) {
    if (a.indexOf(a[i]) != i) a.splice(i, 1)
}
console.log(‘1.自己重复判断\n‘, a);

//新数组重复判断
var b = []
arr.forEach((e, i) => {
    if (b.indexOf(e) == -1) b.push(e)
});
console.log(‘2.新数组重复判断\n‘, b);

//es6 set
a = [...arr]
b = []
b = [...new Set(a)]
console.log(‘3.set\n‘, b); //new Set(a):Set { 1, 4, 2, 5, 6, ‘2‘, 3 }

//fillter
b = []
b = arr.filter((e, i) => arr.indexOf(e) == i)
console.log(‘4.fillter\n‘, b);

//对象属性
var c = {}
b = []
arr.forEach(e => {
    if (!c[e]) {
        c[e] = true
        b.push(e)
    }
})
console.log(‘5.对象属性\n‘, b);
//sort 相邻比较
a = [...arr]
a.sort() //重写排序规则解决字符问题
a.reduceRight((t, e, i) => {
    if (e == a[i + 1]) a.splice(i + 1, 1)
})
console.log(‘6.sort 相邻比较\n‘, a);