Add span to textnodes so can highlight on pdf text layer

highlight.js

function wrapText(container, text) {
	// Construct a regular expression that matches text at the start or end of a string or surrounded by non-word characters.
	// Escape any special regex characters in text.
	var textRE = new RegExp('(^|\\W)' + text.replace(/[\\^$*+.?[\]{}()|]/, '\\$&') + '($|\\W)', 'm');
	var nodeText;
	var nodeStack = [];

	// Remove empty text nodes and combine adjacent text nodes.
	container.normalize();

	// Iterate through the container's child elements, looking for text nodes.
	var curNode = container.firstChild;

	while (curNode != null) {
		if (curNode.nodeType == Node.TEXT_NODE) {
			// Get node text in a cross-browser compatible fashion.
			if (typeof curNode.textContent == 'string')
				nodeText = curNode.textContent;
			else
				nodeText = curNode.innerText;

			// Use a regular expression to check if this text node contains the target text.
			var match = textRE.exec(nodeText);
			if (match != null) {
				// Create a document fragment to hold the new nodes.
				var fragment = document.createDocumentFragment();

				// Create a new text node for any preceding text.
				if (match.index > 0)
					fragment.appendChild(document.createTextNode(match.input.substr(0, match.index)));

				// Create the wrapper span and add the matched text to it.
				var spanNode = document.createElement('span');
				spanNode.className = 'highlighted';
				spanNode.appendChild(document.createTextNode(match[0]));
				fragment.appendChild(spanNode);

				// Create a new text node for any following text.
				if (match.index + match[0].length < match.input.length)
					fragment.appendChild(document.createTextNode(match.input.substr(match.index + match[0].length)));

				// Replace the existing text node with the fragment.
				curNode.parentNode.replaceChild(fragment, curNode);

				curNode = spanNode;
			}
		} else if (curNode.nodeType == Node.ELEMENT_NODE && curNode.firstChild != null) {
			nodeStack.push(curNode);
			curNode = curNode.firstChild;
			// Skip the normal node advancement code.
			continue;
		}

		// If there's no more siblings at this level, pop back up the stack until we find one.
		while (curNode != null && curNode.nextSibling == null)
			curNode = nodeStack.pop();

		// If curNode is null, that means we've completed our scan of the DOM tree.
		// If not, we need to advance to the next sibling.
		if (curNode != null)
			curNode = curNode.nextSibling;
	}
}