call/ec implemented in JS

call_ec.js

function call_ec(f) {
    var tag = new EvalError('Continuation block no loger exists');
    try {
        f(function(rv) {
            tag.rv = rv;
            throw tag;
        });
    } catch(obj) {
        if(obj === tag) {
            return tag.rv;
        }
        throw obj;
    }
};