A JavaScript function is a set of statements that takes inputs, performs specific computations, and produces outputs. Essentially, a function performs tasks or computations and then returns 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 greetUser(username) {
console.log(`Hello ${username}, welcome to GeeksforGeeks`);
}
greetUser('Admin');
OutputHello Admin, welcome to GeeksforGeeks
The Complete List of JavaScript Functions & Properties
JavaScript Function Parameters:
Parameters | Description |
|---|
| Function | The function definition and real values passed to the function in the function definition are known as arguments. |
| Rest | Improved way to handle function parameters defined, allowing us to more easily handle various inputs as parameters in a function. |
| 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. |
JavaScript Functions Properties:
Properties | Description |
|---|
| length | Return the number of parameters required by a function. |
| displayName | Set the display name of the function. |
| caller | Returns the function that invoked the specified function. |
| name | Return the name of the function. |
JavaScript Functions:
Functions | Description |
|---|
| apply() | It is different from the function call() because it takes arguments as an array. |
| isFinite() | It returns true for all the values except +infinity, -infinity, or NaN. |
| isNaN() | It returns true if the value is a NaN else returns false. |
| unescape() | It decodes that string encoded by the escape() function. |
| escape() | It can be transmitted to any computer in any network which supports ASCII characters. |
| number() | Convert the data type to a number. |
| map() | The calling function for each and every array element in an array. |
| String() | Convert the value of an object to a string value. |
| eval() | If the argument represents one or more JavaScript statements, eval() evaluates the statements. |
| uneval() | Create a string representation of the source code of an Object. |
| parseInt() | Accept the string and radix parameters and convert them into an integer. |
| parseFloat() | Accept the string and convert it into a floating-point number. |
| 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. |
Basics of Functions:
JavaScript Operations on Function | Description |
|---|
| Function Generator | It needs to generate a value, it does so with the yield keyword rather than return. |
| Function Binding | In JavaScript, function binding happens using bind() method. |
| Function Invocation | It is common to use the term “call a function” instead of “invoke a function”. |
| Function Expression | Create an anonymous function that doesn’t have any function name. |
| Arrow Functions | Provide generator functions with a concise way to write functions in JavaScript. |
| Async Function | It checks that we are not breaking the execution thread. |
| Pure Functions | Returns the same result if the same arguments are passed. |
| Nested Functions | Return is a combination of the output from the outer as well as the inner function(nested function). |
Understanding JavaScript functions is fundamental for effective programming. These functions and properties enable you to write cleaner, more efficient, and reusable code. For more advanced JavaScript tutorials and examples, explore our JavaScript Tutorial and JavaScript Examples.
