Javascript images preloading by chunks with lodash

gistfile1.js

//requires lodash
function preload(sources, chunkSize) {
    chunkSize = chunkSize || sources.length;
    var sourcesChunked = _.chunk(sources, chunkSize);
    var steps = sourcesChunked.length;
    var current = 0;
    var inner = function(_current){
        var imagesTemp = [];
        var l = sourcesChunked[_current].length;
        var counter = 0;
        var callback = function(){
            console.log("updated counter");
                counter++;
                if(counter == l - 1){
                    if(_current < steps - 1){
                        inner(++_current);
                    }
                    else {
                        // preloading done
                    }
                }
        };
        for (var i = 0; i < l; i++){
            imagesTemp[i] = new Image();
	          imagesTemp[i].src = sourcesChunked[_current][i];
            imagesTemp[i].onload = callback;
        }
    };
    inner(current);
}