A faster version of prism line highlight.

prism-line-highlight.js

(function(){

if (typeof self === 'undefined' || !self.Prism || !self.document || !document.querySelector) {
	return;
}

function $$(expr, con) {
	return Array.prototype.slice.call((con || document).querySelectorAll(expr));
}

function hasClass(element, className) {
  className = " " + className + " ";
  return (" " + element.className + " ").replace(/[\n\t]/g, " ").indexOf(className) > -1
}

// Some browsers round the line-height, others don't.
// We need to test for it to position the elements properly.
var isLineHeightRounded = (function() {
	var res;
	return function() {
		if(typeof res === 'undefined') {
			var d = document.createElement('div');
			d.style.fontSize = '13px';
			d.style.lineHeight = '1.5';
			d.style.padding = 0;
			d.style.border = 0;
			d.innerHTML = '&nbsp;<br />&nbsp;';
			document.body.appendChild(d);
			// Browsers that round the line-height should have offsetHeight === 38
			// The others should have 39.
			res = d.offsetHeight === 38;
			document.body.removeChild(d);
		}
		return res;
	}
}());

function makeActions() {
	var actions = [];

	return {
		actions: actions,
		apply: function(fn, context, args){
			actions.push(function(){
				fn.apply(context, args);
			});
		},
		set: function(obj, key, value) {
			actions.push(function(){
				obj[key] = value;
			});
		}
	};
}

function highlightLines(pre, lines, classes) {
	lines = typeof lines === 'string' ? lines : pre.getAttribute('data-line');

	var ranges = lines.replace(/\s+/g, '').split(','),
	    offset = +pre.getAttribute('data-line-offset') || 0;

	var parseMethod = isLineHeightRounded() ? parseInt : parseFloat;
	var lineHeight = parseMethod(getComputedStyle(pre).lineHeight);
	var hasLineNumbers = hasClass(pre, 'line-numbers');
	var action = makeActions();

	for (var i=0, currentRange; currentRange = ranges[i++];) {
		var range = currentRange.split('-');

		var start = +range[0],
		    end = +range[1] || start;

		var line = pre.querySelector('.line-highlight[data-range="' + currentRange + '"]') || document.createElement('div');

		// line.setAttribute('aria-hidden', 'true');
		action.apply(line.setAttribute, line,['aria-hidden', 'true']);
		// line.setAttribute('data-range', currentRange);
		action.apply(line.setAttribute, line,['data-range', currentRange]);

		line.className = (classes || '') + ' line-highlight';

		//if the line-numbers plugin is enabled, then there is no reason for this plugin to display the line numbers
		if(hasLineNumbers && Prism.plugins.lineNumbers) {
			var startNode = Prism.plugins.lineNumbers.getLine(pre, start);
			var endNode = Prism.plugins.lineNumbers.getLine(pre, end);

			if (startNode) {
				// line.style.top = startNode.offsetTop + 'px';
				action.set(line.style, "top",  startNode.offsetTop + 'px');
			}

			if (endNode) {

				//line.style.height = (endNode.offsetTop - startNode.offsetTop) + endNode.offsetHeight + 'px';
				action.set(line.style, "height", (endNode.offsetTop - startNode.offsetTop) + endNode.offsetHeight + 'px' );
			}
		} else {

			// line.setAttribute('data-start', start);
			action.apply(line.setAttribute, line, ['data-start', start]);

			if(end > start) {
				// line.setAttribute('data-end', end);
				action.apply(line.setAttribute, line, ['data-end', end]);
			}

			//line.style.top = (start - offset - 1) * lineHeight + 'px';
			action.set(line.style, "top", (start - offset - 1) * lineHeight + 'px' );

			action.set(line, "textContent", new Array(end - start + 2).join(' \n') );
		}

		//allow this to play nicely with the line-numbers plugin
		if(hasLineNumbers) {
			//need to attack to pre as when line-numbers is enabled, the code tag is relatively which screws up the positioning
			// pre.appendChild(line);
			action.apply( pre.appendChild, pre, [line] );
		} else {
			action(pre.appendChild, pre.querySelector('code') || pre, [line]);
		}
	}
	return action.actions;
}

function applyHash() {
	var hash = location.hash.slice(1);

	// Remove pre-existing temporary lines
	$$('.temporary.line-highlight').forEach(function (line) {
		line.parentNode.removeChild(line);
	});

	var range = (hash.match(/\.([\d,-]+)$/) || [,''])[1];

	if (!range || document.getElementById(hash)) {
		return;
	}

	var id = hash.slice(0, hash.lastIndexOf('.')),
	    pre = document.getElementById(id);

	if (!pre) {
		return;
	}

	if (!pre.hasAttribute('data-line')) {
		pre.setAttribute('data-line', '');
	}

	var actions = highlightLines(pre, range, 'temporary ');
	actions.forEach(function(action){
		action();
	})

	document.querySelector('.temporary.line-highlight').scrollIntoView();
}

var fakeTimer = 0; // Hack to limit the number of times applyHash() runs

Prism.hooks.add('before-sanity-check', function(env) {
	var pre = env.element.parentNode;
	var lines = pre && pre.getAttribute('data-line');

	if (!pre || !lines || !/pre/i.test(pre.nodeName)) {
		return;
	}

	/*
	* Cleanup for other plugins (e.g. autoloader).
	 *
	 * Sometimes <code> blocks are highlighted multiple times. It is necessary
	 * to cleanup any left-over tags, because the whitespace inside of the <div>
	 * tags change the content of the <code> tag.
	 */
	var num = 0;
	$$('.line-highlight', pre).forEach(function (line) {
		num += line.textContent.length;
		line.parentNode.removeChild(line);
	});
	// Remove extra whitespace
	if (num && /^( \n)+$/.test(env.code.slice(-num))) {
		env.code = env.code.slice(0, -num);
	}
});

Prism.hooks.add('complete', function completeHook(env) {
	var pre = env.element.parentNode;
	var lines = pre && pre.getAttribute('data-line');

	if (!pre || !lines || !/pre/i.test(pre.nodeName)) {
		return;
	}

	clearTimeout(fakeTimer);

	var hasLineNumbers = Prism.plugins.lineNumbers;
	var isLineNumbersLoaded = env.plugins && env.plugins.lineNumbers;

	if (hasClass(pre, 'line-numbers') && hasLineNumbers && !isLineNumbersLoaded) {
		Prism.hooks.add('line-numbers', completeHook);
	} else {
		var actions = highlightLines(pre, lines);
		actions.forEach(function(action){
			action();
		})
		fakeTimer = setTimeout(applyHash, 1);
	}
});

	window.addEventListener('hashchange', applyHash);
	window.addEventListener('resize', function () {
		var preElements = document.querySelectorAll('pre[data-line]');
		var now = new Date();
		var actions = [];
		Array.prototype.forEach.call(preElements, function (pre) {
			actions.push.apply(actions, highlightLines(pre) );
		});
		actions.forEach(function(action){
			action();
		});
		console.log("time", new Date() - now);
	});

})();