javascript - Speed/efficiency of multiple DOM appendChild

Question

I have to create seven div elements in one hit - container A which contains A1, A2, A3 & A4, and then A2a & A2b within A2. I am using multiple calls to this little function:

function u1(t,i,c,p){ // type,id,class_name,parent_id
    var tag=document.createElement(t); // Create node to be appended
    tag.id=i;
    tag.className=c;
    document.getElementById(p).appendChild(tag);
}

My question: Is there is a more time-efficient way to bundle the seven together, and then just do one DOM append? Or is innerHTML a good option?

Thanks :)

Answer 1

You could just use .innerHTML. An alternative would be to use a document fragment:

var fragment = document.createDocumentFragment();

function u1(t, i, c){ // type,id,class_name
    var tag = document.createElement(t); // Create node to be appended
    tag.id = i;
    tag.className = c;
    fragment.appendChild(tag); // will use `fragment` from the outer scope
}

// call u1() seven times

// then insert all the elements into the DOM all at once
document.getElementById('foo').appendChild(fragment);

Document fragments are a bit slow to create, but can save performance in the long run. In this case, for example, you go from 7 DOM insertions to just one. (Anything involving the DOM is slow in JavaScript.)

If you want to benchmark your specific use case using both approaches, create a jsPerf test case.