Micro template engine in JS.

templar.js

var tplNgn = function(qs, opts) {
    var html = document.querySelector(qs).innerHTML;
    var re = /<%([^%>]+)?%>/g;
    var reExp = /(^( )?(if|for|else|switch|case|break|{|}))(.*)?/g;
    var code = 'var r=[];\n';
    var cursor = 0;
    var match;
    var add = function(line, js) {
        if (js) {
            code += (line.match(reExp))
                ? line + '\n'
                : 'r.push(' + line + ');\n';
        } else {
            code += (line != '')
                ? 'r.push("' + line.replace(/"/g, '\\"') + '");\n'
                : '';
        };
        return add;
    };
    while (match = re.exec(html)) {
        add(html.slice(cursor, match.index))(match[1], true);
        cursor = match.index + match[0].length;
    };
    add(html.substr(cursor, html.length - cursor));
    code += 'return r.join("");';
    return new Function(code.replace(/[\r\t\n]/g, '')).apply(opts);
};