The json object is

var data = [{Parent:1,Child:[4,5,6]},{Parent:2},{Parent:3}]

How can I use underscore.js chain/map/pluck etc... function to get the flatten result

     var result = [];

for (var i = 0; i < data.length; i++) {

    result.push(data[i].Parent);

    if (data.Child != undefined) {

        for (var j = 0; j < data[i].Child.length; j++) {

            result.push(data[i].Child[j]);

        }

    }

}

console.log(result) >> //1,4,5,6,2,3