Extend String prototype to include a subs method to interpolate a string

stringInterpolation.js

// From Douglas Crockford's http://javascript.crockford.com/remedial.html
//
// Usage:
// var person = { name: "James", age: 22 };
// var template = "Hello {name}, how does it feel to be {age}?";
// var personalGreeting = template.subs(person);
//     => "Hello James, how does it feel to be 22?"

if (!String.prototype.subs) {
    String.prototype.subs = function (o) {
        return this.replace(/{([^{}]*)}/g,
            function (a, b) {
                var r = o[b];
                return typeof r === 'string' || typeof r === 'number' ? r : a;
            }
        );
    };
}