JavaScript function is reusable piece of code that can be coded once and reused many times. For example, we can create a function that will either switch ON or OFF the lights and then reuse this function by switching the button to ON or OFF
Syntax of Creating a JavaScript Function
function SWITCH(INPUT)
{
Read the INPUT and perform any action, for example SWITCH ON or SWITCH OFF
}
- function is a JavaScript keyword
Example of JavaScript Function Creation
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//function definition function add(a, b) { c = a + b return c } |
- In above example we created a function and named it add. This function is expecting two value
- function is a JavaScript keyword, so we must type it ‘as it is’
- Function values also known as input parameters are always enclosed in parentheses ( ) and separated by comma
- When creating a function we can specify as many input values as we like.
- The action of a function is defined in curly braces { }
- This function will add value of a to value of b and then save the result in c
- This function will provide us the answer by using a keyword return
Syntax of Using a JavaScript Function
SWITCH(INPUT)
- In order to use a function simply type the name of function and pass it the values it is expecting from us.
- For switching lights function it’s expecting one value from us, either ON or OFF
- Once a function is created, we can use it as many times as we like
Example of JavaScript Function Usage
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add(4, 5) |
- In above example we are using (also known as calling) the function add
- we are sending two input values (also known as parameters) of 4 and 5 to our function.
- function parameter are enclosed in parentheses ( ) and separated by a comma ,
- the above example will result in 9