數組去重

data = [{'userId':1,'a':11},{'userId':3,'a':33},{'userId':2,'a':22},{'userId':1,'a':11}]
var hash = [];
var obj = {};
$.each(data,function (i,item) {
    if(!obj[item.userId]){
        obj[item.userId]  = item;
        hash.push(item);
    }
});
console.log(obj);
console.log(hash);