JavaScript: Unveiling the Power and Limitations
4 mins read Published On: Thu Jan 18 2024

JavaScript, often abbreviated as JS, is a versatile programming language widely used in web development. As you embark on your journey into the world of JavaScript, it’s essential to understand its capabilities and limitations. In this blog post, we’ll explore some fundamental aspects of JavaScript that every developer should be aware of.

JS Limitations

JavaScript is a powerful language, but it does come with some limitations that you should keep in mind:

1. No Access to OS Functions

JavaScript does not have access to operating system functions. This means you can’t use JS to automate tasks like turning on your computer at a specific time.

2. Restricted File Access

When running on a webpage, JS cannot read, write, or execute arbitrary files on the user’s hard disk. However, there are some exceptions, such as allowing users to drop files into a window or selecting files using input tags.

3. Same Origin Policy

Different browser tabs/windows do not have awareness of each other. Even if they did, when you open an anchor tag with a target attribute set to “_blank,” one page may not access another page if they come from different websites. This is known as the Same Origin Policy.

JS Basics Before You Start Coding

Before diving into JavaScript coding, it’s crucial to understand where you can place your JS code:

  1. Inside the HTML Document: You can embed JS code within the HTML document, typically in the header section, using a script tag.

  2. Outside the HTML Document: Alternatively, you can place your JS code in an external file and link it to your HTML document using the script tag’s src attribute.

Some Key Points:

  • A single script tag cannot have both src and inline code.
  • The type attribute used for specifying JavaScript is less relevant in modern web development.
  • The language attribute serves the same purpose as type.

Pro Tip: Separate JS Files for Efficiency

For more complex scripts, it’s recommended to put your JavaScript code in a separate file. This allows the browser to download and cache the file, reducing the need to download it multiple times when referenced by multiple HTML documents.

The “strict” Keyword

Introduced in ES5 in 2009, the “strict” mode in JavaScript adds new features and modifies existing ones. However, it is not automatically enabled to maintain compatibility with legacy code. Developers can enable it explicitly using "use strict".

Key Points:

  • Only comments can precede the "use strict" statement; code before it will not enable strict mode.
  • Once enabled, there’s no way to cancel strict mode.
  • In most browsers’ consoles, strict mode is off by default.

Should You Use the Strict Keyword?

Strict mode is beneficial if your code does not heavily rely on advanced language structures like classes and modules. In many cases, these advanced features automatically enable strict mode, making it unnecessary to include it explicitly.

Variables, Data Types, and Interactions

JavaScript handles variables, data types, and interactions in a unique way. Let’s explore these aspects:

Interactions

Modal windows are mini-windows that appear on a webpage. They require user interaction before allowing interaction with the rest of the page. Modals are commonly used for messages or prompts.

Prompt

The prompt function in JavaScript displays a modal window with a user-input field. It takes two parameters: the title (text to show) and an optional default value. If the user cancels the prompt, it returns null; otherwise, it returns the user’s input.

Pro Tip: Handling prompt in IE

In Internet Explorer, it’s essential to use the second parameter (default value) with the prompt function to prevent issues with undefined input fields.

Limitations with Modals

  1. The exact location and appearance of modal windows are determined by the browser, limiting customization options.

Data Types

JavaScript supports various data types, including:

  1. String
  2. Number
  3. Boolean
  4. Null
  5. Undefined
  6. Symbol
  7. BigInt

Additionally, reference data types include Objects, Arrays, Functions, and more.

Variables

JavaScript offers three types of variables:

  1. let: Block-scoped and reassignable.
  2. const: Block-scoped and constant; once assigned, it cannot be reassigned, but its value can be modified for reference types.
  3. var: Function or global-scoped and reassignable.

Understanding the differences in scope and usage among these variables is essential for effective JavaScript programming.

In conclusion, JavaScript is a powerful language with its own set of limitations and intricacies. By grasping these fundamentals, you’re on your way to becoming a proficient JavaScript developer. Stay tuned for more in-depth insights into the world of web development with JavaScript!