//items array 

var items = [{id:1, name:'bill'}, {id:2, name:'sam'}, {id:3, name: 'mary'}, {id:4, name:'jane'}]

​

//sort order array

var order = [{id:1, sortindex:4}, {id:2, sortindex:2}, {id:3, sortindex: 1}, {id:4, sortindex:3}]

​

​

var sortedOrder = _.sortBy(order, 'sortindex');

​

var bb = _.map(sortedOrder, function (i) {

    return i.id;

})

​

var sorted = [];

​

for (var i = 0, ii = bb.length; i < ii; i++) {

    for (var m = 0, mm = items.length; m < mm; m++) {

        var a = items[m];

        if (a.id == bb[i]) {

            sorted.push(items[m]);

        }

    }

}

​

console.log(sorted);