JavaScript pass by reference and pass by value.

This post is about pass by value and pass by reference in JavaScript. Before going into a topic we need to recall things.

In the major programming language, there are two types of data types.

Primitive are predefined datatypes. They are immutable. In JavaScript the primitive data types are

1.Boolean

2.null

3.undefined

4.Number

5.String

6.Symbol

non-primitive datatypes are user define data type. they are mutable in general. In JavaScript Object is Non-Primitive. It is widely used in JavaScript.Objects are defined as key-pair value.

All the primitive data types in JavaScript are pass by value in nature. Their value won’t change if we pass as a parameter to function.

In the above code the variable copy creates new memory assigns the value. therefore there is no contact between orig and copy.

Object are pass by reference in JavaScript. when you assign an object to another variable it won’t create new memory. instead it just refer to original object memory.

In the above code an object is defined in obj and assigned to obj1. whenever obj1 value got changed it also affect obj. Even the changes made in obj will affect the variables refer to obj.

Note: only the data inside the object is non-primitive not the variable.

There are few tricks to prevent an object from being pass are reference.

Some library like underscores have functions to clone…

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