Javascript Object Oriented Design - Javascript Primitive

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Javascript primitive types stores data in memory as it is.

There are five primitive types in JavaScript:

The last two, null and undefined, are special to Javascript.

Null and undefined has their own type of category.

undefined is the value assigned to a variable that is not initialized.

Literals

All primitive types have literal representations of their values.

The following are String literal:

// strings 
var name = "Javascript"; 
var s = "a"; 

name and s are two variables.

Number literal,

// numbers 
var count = 2; 
var cost = 12.251; 

Boolean literal

// boolean 
var found = true; 
var isValid = false;

Null Literal

// null 
var object = null; 

Undefined literal

// undefined 
var flag = undefined; 
var ref;    // assigned undefined automatically 

ref is assigned to value undefined since the variable ref is not assigned to any value.

When assigning a primitive value to a variable, the value is copied into that variable.

When assigning one variable equal to another, each variable gets its own copy of the data.

For example:

var string1 = "pink"; 
var string2 = string1; 

In the code above the 'pink' value is copied to string2 during the assignment.

The following code shows that changes to one variable are not reflected on the other.

For example:

var string1 = "red"; 
var string2 = string1; 
/*from   w  w  w. j  a v  a 2s  .c o  m*/
console.log(string1);    // "red" 
console.log(string2);    // "red" 

string1 = "blue"; 
console.log(string1);    // "blue" 
console.log(string2);    // "red" 

The code above generates the following result.

In this code, string1 is changed and string2 retains its original value.

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