Simple string interpolation

String.subs.js

// use: String.subs('There is no ${foo} foo', { foo: 'bar' })
String.subs = String.subs || function (str, props) {
	return str.replace(/\$\{([^{}]*)}/g, function (a, b) {
        var r = props[b];
        return typeof r === 'string' || typeof r === 'number' ? r : a;
    });
};