extracted template engine from underscore

template.js

var _ = {};
// By default, Underscore uses ERB-style template delimiters, change the
// following template settings to use alternative delimiters.
_.templateSettings = {
    evaluate: /<%([\s\S]+?)%>/g,
    interpolate: /<%=([\s\S]+?)%>/g,
    escape: /<%-([\s\S]+?)%>/g
};

// When customizing `templateSettings`, if you don't want to define an
// interpolation, evaluation or escaping regex, we need one that is
// guaranteed not to match.
var noMatch = /.^/;

// Certain characters need to be escaped so that they can be put into a
// string literal.
var escapes = {
    '\\': '\\',
    "'": "'",
    'r': '\r',
    'n': '\n',
    't': '\t',
    'u2028': '\u2028',
    'u2029': '\u2029'
};

for (var p in escapes) escapes[escapes[p]] = p;
var escaper = /\\|'|\r|\n|\t|\u2028|\u2029/g;
var unescaper = /\\(\\|'|r|n|t|u2028|u2029)/g;

// Within an interpolation, evaluation, or escaping, remove HTML escaping
// that had been previously added.
var unescape = function(code) {
    return code.replace(unescaper, function(match, escape) {
        return escapes[escape];
    });
};

// 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) {
    settings = settings || _.templateSettings;

    // Compile the template source, taking care to escape characters that
    // cannot be included in a string literal and then unescape them in code
    // blocks.
    var source = "__p+='" + text.replace(escaper, function(match) {
        return '\\' + escapes[match];
    }).replace(settings.escape || noMatch, function(match, code) {
        return "'+\n_.escape(" + unescape(code) + ")+\n'";
    }).replace(settings.interpolate || noMatch, function(match, code) {
        return "'+\n(" + unescape(code) + ")+\n'";
    }).replace(settings.evaluate || noMatch, function(match, code) {
        return "';\n" + unescape(code) + "\n;__p+='";
    }) + "';\n";

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

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

    var render = new Function(settings.variable || 'obj', '_', source);
    if (data) return render(data, _);
    var template = function(data) {
        return render.call(this, data, _);
    };

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

    return template;
};

document.write(_.template("<%=name%>", {
    name: "bob"
}));
console.log(_.template("<%=name%>", {
    name: "bob"
}))​