去重

var users = [
    {id: 1, name: 'a'},
    {id: 2, name: 'a'},
    {id: 3, name: 'b'},
    {id: 4, name: 'b'}
]

Array.prototype.unique = function() {
    var obj = {}, arr = [];
    var context = this, name;
    for(var i = 0; i < context.length; i++) {
        name = context[i].name;
        if(!obj[name]) {
            obj[name] = 1;
            arr.push(name);
        }
    }
    return arr;
}

users.unique();