JavaScript functions are used to perform operations. We can call JavaScript function many times to reuse the code.

Advantage of JavaScript function

There are mainly two advantages of JavaScript functions.

  1. Code reusability: We can call a function several times so it save coding.
  2. Less coding: It makes our program compact. We don’t need to write many lines of code each time to perform a common task.

JavaScript Function Syntax

The syntax of declaring function is given below.

function functionName([arg1, arg2, ...argN]){  
 //code to be executed  
}

JavaScript Functions can have 0 or more arguments.

JavaScript Function Example

Let’s see the simple example of function in JavaScript that does not has arguments.

Output of the above example

JavaScript Function Arguments

We can call function by passing arguments. Let’s see the example of function that has one argument.



Output of the above example








Function with Return Value


We can call function that returns a value and use it in our program. Let’s see the example of function that returns value.


  



Output of the above example


hello codebridgeplus! How r u?




JavaScript Function Object


In JavaScript, the purpose of Function constructor is to create a new Function object. It executes the code globally. However, if we call the constructor directly, a function is created dynamically but in an unsecured way.


Syntax


new Function ([arg1[, arg2[, ....argn]],] functionBody)


Parameter


arg1, arg2, …. , argn – It represents the argument used by function.


functionBody – It represents the function definition.


JavaScript Function Methods


Let’s see function methods with description.






Method
Description




apply()
It is used to call a function contains this value and a single array of arguments.




bind()
It is used to create a new function.




call()
It is used to call a function contains this value and an argument list.




toString()
It returns the result in a form of a string.








JavaScript Function Object Examples


Example 1


Let’s see an example to display the sum of given numbers.




Output:




7





Example 2


Let’s see an example to display the power of provided value.




Output:




8