Question

Simple question, I have an element which I am grabbing via .getElementById (). How do I check if it has any children?

Answer 1

A couple of ways:

if (element.firstChild) {
    // It has at least one
}

or the hasChildNodes() function:

if (element.hasChildNodes()) {
    // It has at least one
}

or the length property of childNodes:

if (element.childNodes.length > 0) { // Or just `if (element.childNodes.length)`
    // It has at least one
}

If you only want to know about child elements (as opposed to text nodes, attribute nodes, etc.) on all modern browsers (and IE8 — in fact, even IE6) you can do this: (thank you Florian!)

if (element.children.length > 0) { // Or just `if (element.children.length)`
    // It has at least one element as a child
}

That relies on the children property, which wasn’t defined in DOM1, DOM2, or DOM3, but which has near-universal support. (It works in IE6 and up and Chrome, Firefox, and Opera at least as far back as November 2012, when this was originally written.) If supporting older mobile devices, be sure to check for support.

If you don’t need IE8 and earlier support, you can also do this:

if (element.firstElementChild) {
    // It has at least one element as a child
}

That relies on firstElementChild. Like children, it wasn’t defined in DOM1-3 either, but unlike children it wasn’t added to IE until IE9. The same applies to childElementCount:

if (element.childElementCount !== 0) {
    // It has at least one element as a child
}

If you want to stick to something defined in DOM1 (maybe you have to support really obscure browsers), you have to do more work:

var hasChildElements, child;
hasChildElements = false;
for (child = element.firstChild; child; child = child.nextSibling) {
    if (child.nodeType == 1) { // 1 == Element
        hasChildElements = true;
        break;
    }
}

All of that is part of DOM1, and nearly universally supported.

It would be easy to wrap this up in a function, e.g.:

function hasChildElement(elm) {
    var child, rv;

    if (elm.children) {
        // Supports `children`
        rv = elm.children.length !== 0;
    } else {
        // The hard way...
        rv = false;
        for (child = element.firstChild; !rv && child; child = child.nextSibling) {
            if (child.nodeType == 1) { // 1 == Element
                rv = true;
            }
        }
    }
    return rv;
}