原文：https://github.com/mqyqingfeng/Blog/issues/27

indexOf 去重

var array = [1, 1, '1'];

function unique(array) {
    var res = [];
    for (var i = 0, len = array.length; i < len; i++) {
        var current = array[i];
        if (res.indexOf(current) === -1) {
            res.push(current)
        }
    }
    return res;
}

console.log(unique(array));

使用filter中的indexOf
var array = [1, 2, 1, 1, '1'];

function unique(array) {
var res = array.filter(function(item, index, array){
return array.indexOf(item) === index;
})
return res;
}

console.log(unique(array));

var array = [1, 2, 1, 1, '1'];

function unique(array) {
return Array.from(new Set(array));
}

==》

function unique(array) {
return [...new Set(array)];
}