JavaScript function statements

Examples

Declare a function, the function call output "Hello World" on the id = "demo" element:

function myFunction () {// declare a function
document.getElementById ( "demo") innerHTML = "Hello World!".;
}

myFunction (); // call the function

try it"

Bottom of this article contains more examples.

Definition and Usage

function statement to declare a function.

After the function declaration, we can call on when needed.

In JavaScript, functions are objects, functions also have properties and methods.

Function can also be defined by the expression (you can view the function definition ).

Please read our JavaScript tutorials to learn more about the function of the content. First, we can first understand JavaScript function and JavaScript scope . You can view more detailed data about the function definition , parameters , call and closures .

Tip: Use the return statement to return value of the function.

Browser Support

Statements
function	Yes	Yes	Yes	Yes	Yes

grammar

functionfunctionName (parameter s) {
Code execution
}

Parameter Value

parameter	description
functionName	have to. Specifies the name of the function. The function name can contain letters, numbers, underscores, and dollar sign (variable naming conventions as well)
parameters	Optional. Specifies the name of one or more parameters, a plurality of parameters can be a comma (,) separated. Function when the real value of the received call. Inside the function, the parameters are local variables. Note: If not specified when calling the function parameter for the specified parameter value is set to undefined

technical details

JavaScript version:	1.0

More examples

Examples

Returns the value of PI:

function myFunction () {
return Math.PI;
}

Output:

3.141592653589793

try it"

Examples

Returns a ride on the value of b:

function myFunction (a, b) {
return a * b;
}

try it"

Examples

The function is called using different parameters, output different results.

Convert Fahrenheit to Celsius:

function toCelsius (fahrenheit) {
return (5/9) * (fahrenheit-32);
}

try it"

Examples

Function can be used as a variable.

Instead of:

temp = toCelsius (32);
text = "The temperature is" + temp + "Centigrade";

You can also do this:

text = "The temperature is" + toCelsius (32) + "Centigrade";

try it"

Examples

JavaScript function has a built-in object arguments.

arguments.length property returns a function call when receiving the number of parameters:

function myFunction (a, b) {
return arguments.length;
}

try it"

Examples

Click the button to call the function after the function will output "Hello World" on the id = "demo" element:

<Button onclick = "myFunction ()"> Click me </ button>

<P id = "demo"> </ p>

<Script>
function myFunction () {
. Document.getElementById ( "demo") innerHTML = "Hello World";
}
</ Script>

try it"