Safely resolve string-form variable references.

resolve.js

(function(scope) {

    var resolve = scope.resolve = function(reference, context) {
        if (resolve.RE.test(reference)) {
            return resolve.unsafe(reference, context);
        }
    };
    resolve.RE = /^([\w\$]+)?((\.[\w\$]+)|\[(\d+|'(\\'|[^'])+'|"(\\"|[^"])+")\])*$/;

    resolve.unsafe = function(reference, context) {
        context = context || scope;
        try {
            return eval('context'+(reference.charAt(0) !== '[' ? '.'+reference : reference));
        } catch (e) {}
    };

    resolve.or = function(reference, context) {
        var value = resolve(reference, context);
        return value === undefined ? reference : value;
    }

})(this);