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Friday, October 31, 2014

Things you may not know about Javascript

Object Literal provide a very convenient notation for creating new object values. An object literal is a pair of curly braces surrounding zero or more name/value pairs.

var empty_obj={};
var stooage={"firstname":"Gen","lastname":"Linux"}

Objects can nest.

var flight={
      air:"BA",number:"335",departure:{Gate:"45"}
}

Undefined value is produced if an attempt is made to retrieve a non-existent member.

stooage.status     // undefined
flight["area]        // undefined

Attempting to retrieve values from undefined will throw a TypeError exception.

flight.equipment         // undefined
flight.equipment.model      // throw "TypeError"

This can be guarded against with the && operator:

flight.equipment && flight.equipment.model       // undefined


Reference

Objects are passed around by reference. They are never copied:

var x=stooge;
x.nickname = 'Curly';
var nick = stooge.nickname;
// nick is 'Curly' because x and stooge

// are references to the same object

Function Literal

Function objects are created with function literals:

// Create a variable called add and store a function
var add = function (a, b) {
return a + b;

};