underscore.js

    // JavaScript micro-templating, similar to John Resig's implementation.
    // Underscore templating handles arbitrary delimiters, preserves whitespace,
    // and correctly escapes quotes within interpolated code.
    _.template = function (text, data, settings) {
        var render;
        settings = _.defaults({}, settings, _.templateSettings);

        // Combine delimiters into one regular expression via alternation.
        var matcher = new RegExp([
          (settings.escape || noMatch).source,
          (settings.interpolate || noMatch).source,
          (settings.evaluate || noMatch).source
        ].join('|') + '|$', 'g');

        // Compile the template source, escaping string literals appropriately.
        var index = 0;
        var source = "__p+='";
        text.replace(matcher, function (match, escape, interpolate, evaluate, offset) {
            source += text.slice(index, offset)
              .replace(escaper, function (match) { return '\\' + escapes[match]; });

            if (escape) {
                source += "'+\n((__t=(" + escape + "))==null?'':_.escape(__t))+\n'";
            }
            if (interpolate) {
                source += "'+\n((__t=(" + interpolate + "))==null?'':__t)+\n'";
            }
            if (evaluate) {
                source += "';\n" + evaluate + "\n__p+='";
            }
            index = offset + match.length;
            return match;
        });
        source += "';\n";

        // If a variable is not specified, place data values in local scope.
        if (!settings.variable) source = 'with(obj||{}){\n' + source + '}\n';

        source = "var __t,__p='',__j=Array.prototype.join," +
          "print=function(){__p+=__j.call(arguments,'');};\n" +
          source + "return __p;\n";

        try {
            render = new Function(settings.variable || 'obj', '_', source);
        } catch (e) {
            e.source = source;
            throw e;
        }

        if (data) return render(data, _);
        var template = function (data) {
            return render.call(this, data, _);
        };

        // Provide the compiled function source as a convenience for precompilation.
        template.source = 'function(' + (settings.variable || 'obj') + '){\n' + source + '}';

        return template;
    };