JavaScript Function Complete Reference

The JavaScript function is a set of statements that take inputs, do some specific computation, and produce output. Basically, a function is a set of statements that performs some tasks or does some computation and then return the result to the user.

Syntax:

function functionName(Parameter1, Parameter2, ..) {
    // Function body
}

Example: Below is a sample program that illustrates the working of functions in JavaScript:

Javascript

// Function definition
function welcomeMsg(name) {
    console.log("Hello " + name
        + " welcome to GeeksforGeeks");
}

// creating a variable
let nameVal = "Admin";

// calling the function
welcomeMsg(nameVal);

Output:

Hello Admin welcome to GeeksforGeeks

The Complete List of JavaScript Functions & Properties are listed below:

JavaScript Function Parameters:

Parameters	Description	Example
Function	The function definition and real values passed to the function in the function definition are known as arguments.	Try
Rest	Improved way to handle function parameters defined, allowing us to more easily handle various inputs as parameters in a function.	Try
Default parameters	In JavaScript, the parameters of functions default to undefined. However, in some situations, it might be useful to set a different default value.	Try

JavaScript Functions  Properties:

Properties	Description	Example
length	Return the number of parameters required by a function.	Try
displayName	Set the display name of the function.	Try
caller	Returns the function that invoked the specified function.	Try
name	Return the name of the function.	Try

JavaScript Functions:

Functions	Description	Example
apply()	It is different from the function call() because it takes arguments as an array.	Try
isFinite()	It returns true for all the values except +infinity, -infinity, or NaN.	Try
isNaN()	It returns true if the value is a NaN else returns false.	Try
unescape()	It decodes that string encoded by the escape() function.	Try
escape()	It can be transmitted to any computer in any network which supports ASCII characters.	Try
number()	Convert the data type to a number.	Try
map()	The calling function for each and every array element in an array.	Try
String()	Convert the value of an object to a string value.	Try
eval()	If the argument represents one or more JavaScript statements, eval() evaluates the statements.	Try
uneval()	Create a string representation of the source code of an Object.	Try
parseInt()	Accept the string and radix parameters and convert them into an integer.	Try
parseFloat()	Accept the string and convert it into a floating-point number.	Try
console.log()	To print any kind of variables defined before in it or to just print any message that needs to be displayed to the user.	Try

Basics of Functions:

JavaScript Operations on Function	Description	Example
Function Generator	It needs to generate a value, it does so with the yield keyword rather than return.	Try
Function Binding	In JavaScript, function binding happens using bind() method.	Try
Function Invocation	It is common to use the term “call a function” instead of “invoke a function”.	Try
Function Expression	Create an anonymous function that doesn’t have any function name.	Try
Arrow Functions	Provide generator functions with a concise way to write functions in JavaScript.	Try
Async Function	It checks that we are not breaking the execution thread.	Try
Pure Functions	Returns the same result if the same arguments are passed.	Try
Nested Functions	Return is a combination of the output from the outer as well as the inner function(nested function).	Try