Type checking in Javascript.

typeCheck.md

    //Function to check type in JS.
    function typeCheck(x) {
        return Object.prototype.toString.call(x);
    }

    //Test Code:
    var x;
    var y = null;

    console.log(typeCheck({}));             //Logs: [object Object]
    console.log(typeCheck([]));             //Logs: [object Array]
    console.log(typeCheck(true));           //Logs: [object Boolean]
    console.log(typeCheck(new Date()));     //Logs: [object Date]
    console.log(typeCheck(Math));           //Logs: [object Math]
    console.log(typeCheck(21));             //Logs: [object Number]
    console.log(typeCheck(""));             //Logs: [object String]
    console.log(typeCheck(x));              //Logs: [object Undefined]
    console.log(typeCheck(y));              //Logs: [object Null]
    console.log(typeCheck(/abcd/));         //Logs: [object RegExp]

    //References:
    //1) http://blog.niftysnippets.org/2010/09/say-what.html
    //2) https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/toString