源码

//方案1，旧方案
Array.prototype.unique = function(key) {
    var arr = this;
    var n = [arr[0]];
    for (var i = 1; i < arr.length; i++) {
        if (key === undefined) {
            if (n.indexOf(arr[i]) == -1) n.push(arr[i]);
        } else {
            inner: {
                var has = false;
                for (var j = 0; j < n.length; j++) {
                    if (arr[i][key]!==undefined && arr[i][key] === n[j][key]) {
                        has = true;
                        break inner;
                    }
                }
            }
            if (!has) {
                n.push(arr[i]);
            }
        }
    }
    return n;
}

//方案2，相比方案一，少了一层循环，提高效率，逻辑更加清晰
Array.prototype.uniqueTree = function(key) {
        var res = [];
        var json = {};
        var arr = this;
        for (var i = 0; i < arr.length; i++) {
            if (arr[i][key]===undefined||json[arr[i][key]]===undefined) {
                res.push(arr[i]);
                json[arr[i][key]] = 1;
            }
        }
        return res;
    };
    

使用方法：

[1,2,3,4,3,2].unique()
//[1,2,3,4]

[{a:1},{a:2},{a:1}].unique('a')
//[{a:1},{a:2}]