How to Run JavaScript in the Browser

A quick and easy guide to running JavaScript in the browser. This guide will show you how to set up your environment and get started with running JavaScript code in the browser.

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Introduction

JavaScript is a programming language that can be used to make websites and web applications more interactive. You can use JavaScript to add new features or change the behavior of existing features on a website.

To use JavaScript in the browser, you first need to create a file with a .js extension. You can then embed JavaScript code in this file and include it in your HTML code using the

To include inline code, use the text content of the element:

The src Attribute

If you want to include a JavaScript file from another location on the web, you can use the src attribute. This allows you to put all of your JavaScript code into a single file that can be referenced from multiple pages on your website.

The src attribute is used to specify the URL of the external JavaScript file. The code in the file will be executed when the

You can also use a relative URL to include a JavaScript file from another location on your own website:

The defer Attribute

The defer attribute is used to specify that the script is executed when the page has finished parsing. This attribute is only used if the src attribute is present.

If you have multiple defer scripts, they will execute in the order that they appear in the document.

This example shows a script that is executed when the page has finished parsing:
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The async Attribute

The async attribute is a boolean attribute that indicates that the browser should, if possible, load the script asynchronously. This means that the script will be fetched in parallel to the browser continuing to parse the page, and it doesn't necessarily wait for its turn in the event loop.

If async is present, then whether the script is fetched asynchronously depends on its attribute values. If async is present but has no value or if its value is an empty string or a case-insensitive match for the string "async", then it defaults to true and loads asynchronously. Otherwise (if async has any other value), it loads synchronously.

In order for this to work properly, you should include the defer attribute as well. The defer attribute is a boolean attribute that indicates that the browser should go on working with the page while loading the script in background, and then execute it when it's complete. If defer is present but has no value or if its value is an empty string or a case-insensitive match for "defer", then it evaluates to true.

Executing Scripts

You can execute or run JavaScript in your browser without having to install any additional software. All you need is a text editor and a web browser. In this article, we'll show you how to run JavaScript in the browser. We'll also provide some tips on how to debug your code so that you can troubleshoot any errors that you may encounter.

Scripts in

The close tag at the end of the page. Scripts placed in the section are executed when the page loads. Scripts placed in the section are executed when they are loaded.

The placement of your script tags can make a difference in when your code is executed. For example, you might want a script to run only after the page has finished loading. In that case, you would place your script tag at the end of the page just before the tag.

When a browser loads a page it loads all elements in the order they appear in the HTML code. This includes scripts, which means that if you place a script tag in the section it will load and execute before any other element on the page, including other scripts.

Scripts in

Including scripts in the body of your HTML document is very simple. All you need to do is write your code between tags. For example:

You can put your script tags anywhere in the section of your HTML document. The browser will read the document from top to bottom, so if you put your script tags at the bottom, near the closing tag, the browser will load (or "parse") the entire HTML document before it runs your code. This can be beneficial because it allows the rest of the page to load faster. However, it also means that if your code depends on elements in the , they might not be available yet when your code runs. In general, it's a good idea to put your script tags near the bottom of your HTML document, just before the closing tag.

Conclusion

Now that you know how to run JavaScript in the browser, you can start using it to build web applications. Remember to include the