var myFunction = function() {
    console.log('hello');
};

var myObject = {
    foo : 'bar'
};

var myArray = [ 'a', 'b', 'c' ];

var myString = 'hello';

var myNumber = 3;

typeof myFunction;   // returns 'function'
typeof myObject;     // returns 'object'
typeof myArray;      // returns 'object' -- careful!
typeof myString;     // returns 'string';
typeof myNumber;     // returns 'number'

typeof null;         // returns 'object' -- careful!


if (myArray.push && myArray.slice && myArray.join) {
    // probably an array
    // (this is called "duck typing")
}

if (Object.prototype.toString.call(myArray) === '[object Array]') {
    // Definitely an array!
    // This is widely considered as the most rebust way
    // to determine if a specific value is an Array.
}