In this blog post, we will be discussing how to write a function in JavaScript. This is a fundamental skill that is necessary for any web developer.
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Introduction
A function is a group of instructions that can be reusable and is often used to perform a specific task. Functions are written in the same language as the code that calls them. In JavaScript, functions are written using the function keyword followed by a name, and they are executed when they are called.
Functions can take input in the form of arguments, and they can return output in the form of return values. Functions can also be written without arguments or return values.
Functions can be defined inside other functions, and they can be invoked from anywhere in your code. When a function is invoked, the code inside the function is executed.
What is a function?
A function is a block of code that performs a specific task. Functions are often “called” or “invoked” by other code. For example, you might call a function to calculate the tax on a purchase, or to format a date for display.
Functions can take arguments, which are values that are passed into the function when it is invoked. The function can then use those arguments to perform its task. For example, a function that calculates the tax on a purchase might take the purchase price as an argument.
Functions can also return values, which are values that the function produces and hands back to the code that invoked it. For example, a function that calculates the tax on a purchase might return the amount of tax due.
How to write a function
A function is a set of statements that take inputs, do some processing, and return an output. Functions are written using the function keyword, like this:
function functionName(parameter1, parameter2) {
// code to be executed
}
Function parameters are the values that are passed to the function when it is invoked. The code inside the function can use the parameter values to do its work. In the example above, the function has two parameters, parameter1 and parameter2.
The code inside the function is enclosed in curly braces {}. This code is executed when the function is invoked. In the example above, the code inside the function simply outputs the string “Hello world!” when it’s run. When you write a function, you can give it a name that describes what it does. In this case, we’ve called our function “functionName”. But you could call it anything you like.
Functions can optionally return a value back to where they were invoked from. In the example above, we didn’t use a return statement, so no value was returned. If we wanted to return a value from our function, we could do it like this:
function addNumbers(a, b) {
return a + b; //returns the sum of a and b back to where addNumbers was invoked
}
The return keyword causes your function to stop running and immediately return a value back to where it was invoked from. In this case, our addNumbers() function returns back the sum of its two input parameters (a + b).
How to call a function
To call a function, you simply type the function’s name followed by parenthesis. Any parameters that the function requires go inside of the parenthesis. A function can have zero or more parameters.
Here is an example of a function with no parameters:
“`
function alert() {
alert(‘Hello, world!’);
}
“`
You would call this function like this:
“`
alert(); // alerts ‘Hello, world!’;
“`
Conclusion
Now that you know the basics of how to write a function in JavaScript, you can start using them to add more interactivity and logic to your webpages. Remember to keep your code organized and easy to read by using clear function names and comments. And don’t forget to test your code thoroughly before publishing it!
