Question

Is there a simpler (or more efficient) way of achieving the following:

var _dataObjects = [{id:0, data:"data0", nextID:1}, 
                    {id:1, data:"data1", nextID:2}, 
                    {id:2, data:"data2", nextID:3} .. etc.];
generateNextPieceOfData();

function generateNextPieceOfData(){
    var len = _dataObjects.length;
    for ( var i = 0; i < len; i ++ ) {
        var nextDataID = _dataObjects[i].nextID;
        var nextData;
        for ( var j = 0; j < len; j ++ ) {
            if( _dataObjects[j].id == nextDataID ){
                nextData = _dataObjects[j].data;
                break;
            }
        }
    }
}

The above example is abstracted from the problem I’m having and I realise the ID numbers are sequential in this instance but in the real problem nextID numbers do not run sequentially.

Thanks in advance.

Answer 1

Use the right data structure for your problem. Since you want to find an object by ID, create a hash map with the IDs as keys and objects as values:

var object_map = {};

for(var i = 0, l = _dataObjects.length; i < l; i++) {
    objects[_dataObjects[i].id] = _dataObjects[i];
}

Then getting the next object is simply:

var next_object = object_map[someObject.nextID];

You still have iterate until some terminal condition is met though. For example:

function generatePath(id_a, id_b) {
    var obj = object_map[id_a];
    var path = [obj];

    while (obj && obj.id !== id_b) {
        obj = object_map[obj.nextID];
        path.push(obj);
    }
    return path;
}