Switch.js

var Switch = function(expr){
        this.successed = false;
        this.case = function(cond, proc){
                if( !this.successed && cond  === expr){
                        this.successed = true;
                        proc();
                }
                return this;
        }
}

var x = 0;

new Switch(true).
        case(x > 0, function(){
              console.log(x + " is positive.");
        }).
        case(x === 0, function(){
        	console.log(x + " is zero. ");
        }).
        case(x < 0 function(){
        	console.log(x + " is negative . ");
        });