How to Use JavaScript in HTML

Contents

Introduction to JavaScript
Basic Syntax
Advanced Syntax
Conclusion
- Further Reading

This tutorial will teach you how to use JavaScript in HTML. You will learn how to add JavaScript to your HTML code and how to use it to make your web pages more interactive.

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Introduction to JavaScript

JavaScript is a programming language that can be used to make web pages more interactive. JavaScript can be used to validate form data, create cookies, detect a user’s browser, and much more. In this article, we will discuss how to use JavaScript in HTML.

What is JavaScript?

JavaScript is a dialect of ECMAScript, standardized by Ecma International. JavaScript is high-level, often just-in-time compiled, and multi-paradigm. It supports object-oriented, procedural, and functional programming styles. Alongside HTML and CSS, it is one of the three essential technologies of dynamic web pages.

What can JavaScript Do?

JavaScript can “display” data in different ways:

-Writing into an HTML element, using innerHTML.
-Writing into the HTML output using document.write().
-Changing the style of an HTML element, using style.
-Changing the content of an attribute, using setAttribute().
-Changing the class name of an element, using className.
-Adding, removing, or toggle HTML elements with createElement(), removeChild(), and appendChild().

How to Use JavaScript in HTML

JavaScript is a programming language that can be used to make web pages more interactive. For example, you can use JavaScript to create an image gallery, create a form for visitors to fill out, or even create games.

If you’re new to programming, don’t worry! You don’t need to be an expert programmer to use JavaScript in your web pages. In fact, all you need to know is how to add a few lines of code to your HTML.

In this article, we’ll show you how to include JavaScript in your HTML files, and how to use some of the most common JavaScript code snippets. By the end of this article, you should have a good understanding of how JavaScript works and be able to use it in your own web pages.

Basic Syntax

To use JavaScript in an HTML document, you must first create a JavaScript file. A JavaScript file is simply a text file with a “.js” extension. This file will contain all JavaScript code that you wish to use. You can then include this file in your HTML document using the script> tag. Let’s look at a simple example.

JavaScript Comments

You can place comments in JavaScript code to make it more readable. Comments can also be used to prevent execution, when testing alternate sections of code.

JavaScript comments can be used to explain JavaScript code, and to make it more readable. Comments can also be used to prevent execution, when testing alternate sections of code.

Single-line comments start with //. All characters between // and the end of the line are ignored by JavaScript (will not be executed).

Multi-line comments start with /* and end with */. Everything between /* and */ will be ignored by JavaScript.

JavaScript Variables

In JavaScript, variables are containers that hold information to be used in a script. Variables can hold many data types, such as strings, numbers, and objects. You can name a variable anything you want, as long as it follows these rules:
-A variable must begin with a letter (a – z), an underscore (_), or a dollar sign ($).
-After the first letter, variables can include any combination of letters (a – z), numbers (0 – 9), or underscores (_).
-JavaScript is case sensitive, meaning that the variable myVar is not the same as the variable myvar.

There are two ways to create a JavaScript variable:

-Using the keyword var: This is the most common way to create a variable in JavaScript. To use this method, you first write the keyword var followed by the name of your variable. For example:
var myName = “John Smith”;
This code creates a new variable called myName and assigns it the value “John Smith”. The value can be a string (text surrounded by quotation marks), number, object, or Boolean (true or false).
-Without using the keyword var: You can also create variables without using the keyword var. For example:
myName = “John Smith”;
This code creates a new variable called myName and assigns it the value “John Smith”. The value can be a string (text surrounded by quotation marks), number, object, or Boolean (true or false).

JavaScript Operators

JavaScript operators are used to perform operations on variables and values.

Operators are assigned specific tasks:

– Arithmetic operators are used in mathematical expressions.
– Assignment operators are used to assign values to variables.
– Comparison operators are used in logical (Boolean) expressions.
– Logical operators are used in logical (Boolean) expressions.
– Bitwise operators are used to perform operations on binary numeric values.

JavaScript Functions

A function is a block of code that takes an input and produces an output. In JavaScript, we can write our own functions or use functions that are built-in to the language.

There are two parts to using a function:

1. Defining the function: this is where we write the code for the function.
2. Calling the function: this is where we tell the browser to run the code that we’ve defined in the function.

Functions are written like this:

function myFunction() {
// code goes here!
}
You’ll notice that there are two curly braces {} surrounding the code inside the function. These braces tell JavaScript where the function starts and ends. Anything inside these braces is considered part of the function.

We can also add inputs to our functions, which are called parameters. These allow us to customize the output of our functions based on different inputs. For example, let’s say we want to write a function that takes a person’s name and says hello to them:

Advanced Syntax

In order to use JavaScript in HTML, you will need to understand how to use advanced syntax. This includes using JavaScript functions, variables, and loops. We will go over all of these topics in this section.

JavaScript Loops

JavaScript Loops are used to execute a block of code repeatedly. The three types of loops used in JavaScript are :
-for loop
-while loop
-do…while loop

A for loop is used when you know how many times the code should run. A while loop is used when you don’t know how many times the code should run. A do…while loop is similar to a while loop, except the code always runs at least once.

JavaScript Arrays

JavaScript arrays are used to store multiple values in a single variable. They are declared using square brackets and values are separated by commas.

var myArray = [1, 2, 3, 4];

Arrays can contain both strings and numbers.

var myArray = [“string”, 1, 2, 3];

You can access individual array elements by using their index number. Index numbers start at 0, so the first element in an array is at index 0. For example:

myArray[0] // returns “string”
myArray[1] // returns 1
myArray[2] // returns 2
myArray[3] // returns 3

You can also add new elements to an array by assigning a value to an index that doesn’t already exist:
myArray[4] = “new element”;

Arrays have a length property that specifies the number of items in the array. For example:

myArray.length // returns 4

Arrays also have methods that can be used to manipulate them. For example, the push() method adds new items to the end of an array:

myArray.push(“new item”);

The pop() method removes the last item from an array:

myArray.pop();

There are many other methods available for arrays; you can find a complete list here.

JavaScript Objects

JavaScript Objects are a powerful way to organize data. You can think of them as being like simple lists, with each item in the list having a name and a value. However, unlike lists, items in JavaScript Objects can be any type of data, not just simple values like numbers or strings.

JavaScript Objects are stored as key-value pairs. The key is like the name of the item in a list, and the value is like the actual value of that item. Values can be any type of data, including other objects. This means that you can store complex data structures in JavaScript objects.

To create a JavaScript Object, you use curly braces ({ }) and inside of those braces you list out the key-value pairs:
“`markdown
var person = {
name: “John Smith”,
age: 30,
address: {
street: “Main Street”,
city: “New York”,
state: “NY”
}
};

Conclusion

JavaScript can be used in a number of ways to improve the appearance and functionality of your web pages. It can be used to create interactive forms, validate form input, create cookies, and much more. In this article, we will cover some of the most common uses of JavaScript in HTML.

How to Use JavaScript in HTML