Highlight text in a webpage based on keywords

highlight.js

keywords = ['hello world','goodbye cruel world'];
function replaceKeywords (domNode) {
    if (domNode.nodeType === Node.ELEMENT_NODE) { // We only want to scan html elements
        var children = domNode.childNodes;
        for (var i=0;i<children.length;i++) {
            var child = children[i];

            // Filter out unwanted nodes to speed up processing.
            // For example, you can ignore 'SCRIPT' nodes etc.
            if (child.nodeName != 'EM') {
                replaceKeywords(child); // Recurse!
            }
        }
    }
    else if (domNode.nodeType === Node.TEXT_NODE) { // Process text nodes
        var text = domNode.nodeValue;

        // This is another place where it might be prudent to add filters

        for (var i=0;i<keywords.length;i++) {
            var match = text.indexOf(keywords[i]); // you may use search instead
            if (match != -1) {
                // create the EM node:
                var em = document.createElement('EM');

                // split text into 3 parts: before, mid and after
                var mid = domNode.splitText(match);
                mid.splitText(keywords[i].length);

                // then assign mid part to EM
                mid.parentNode.insertBefore(em,mid);
                mid.parentNode.removeChild(mid);
                em.appendChild(mid);
            }
        }
    }
}