JavaScript Functions

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.

1. function functionName([arg1, arg2, ...argN]){  
2.  //code to be executed  
3. }  

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.

1. <script>  
2. function msg(){  
3. alert("hello! this is message");  
4. }  
5. </script>  
6. <input type="button" onclick="msg()" value="call function"/>  

Output of the above example

Function Arguments

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

1. <script>  
2. function getcube(number){  
3. alert(number*number*number);  
4. }  
5. </script>  
6. <form>  
7. <input type="button" value="click" onclick="getcube(4)"/>  
8. </form>  

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.

1. <script>  
2. function getInfo(){  
3. return "hello java! How r u?";  
4. }  
5. </script>  
6. <script>  
7. document.write(getInfo());  
8. </script>  

Output of the above example

hello java! How r u?