Why = and not : ?

[javascriptnewbie]

As the title says why do we use = to assign variable a value and not :
Fr instance here, in this function.
Why cannot colon be used instead of equal sign..

packet=new Object();
packet.color=”red”;
packet.type=”plastic”;
packet.size=function(a,b){
return a+b;
}

document.write(packet.size(10,10));

[Alen]

You are venturing into Object Oriented Programming. Read this couple of times before asking anymore question, it’s not that we don’t want to help, it’s because a lot of answers are right there in the text for you.

• Intro to OOP with JavaScript

• Working with Objects

• JavaScript Guide

In short answer to your question.

// Object with literal notation!

obj1 = { name: "Bruce Lee, 1" }
alert(obj1.name); // Bruce Lee, 1

// Object using constructor function!

function Person( name ) {
 this.name = name; }

var obj2 = new Person("Bruce Lee, 2");
alert(obj2.name); // Bruce Lee, 2

http://codepen.io/anon/pen/ukiLF

As you can see with one you are defining literal notation and the other has to be instantiated.

[__]

Specifically, in this case:

packet=new Object();
packet.color = "red";

You have to use = because it’s an assignment. packet.color creates a new property in your object, and = "red" assigns a value to it. The object itself already exists; you’re adding to it.

In contrast:

packet = {
    color: "red"
};

Here, you use : because you’re using a literal notation—you’re defining the entire object, and its properties, together. color: is a label for the object property, which is syntactically (if not practically) different, and "red" is the initial value.

[Author]

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