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Head First Javascript Programming: Javascript Explained

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Javascript is a programming language used to create the interactive experiences found online. It’s fast, versatile, and performs a number of tasks that are essential for modern web design and development. If you’re just starting out as a web developer, getting a handle on Javascript is a must. This article provides an introduction to the basics of Javascript programming, from variables to functions and more.

Introduction to Javascript

Javascript is an interpreted programming language developed in the early 1990s by Brendan Eich. It’s the world’s most used scripting language, and one of the most powerful programming languages available. Javascript code can be embedded into websites or standalone applications, and it can also be used to create dynamic web pages. Javascript enables developers to build interactive elements such as forms, games, and other complex applications.

Javascript is a versatile language that can be used to create a wide range of applications, from simple web pages to complex web applications. It is also used to create mobile applications, desktop applications, and even games. Javascript is a popular language among developers due to its flexibility and ease of use.

The Basics of Javascript Coding

If you’re new to Javascript, here are some things you need to know. Javascript has two parts: the syntax and the environment. The syntax is the way in which something is written, like the grammar of a language. The environment is the web or application where Javascript is being used, such as a browser or mobile phone.

Javascript uses text-based code that’s organized into lines, referred to as statements. Each statement is a command that tells the browser what to do. When you write Javascript, you’re telling the browser how it should respond to certain events, like mouse clicks or keystrokes.

Javascript is an interpreted language, which means that it is read and executed line by line. This makes it easier to debug and modify code, as you can quickly identify and fix errors. It also makes it easier to create dynamic webpages, as you can quickly add new features and content.

Understanding Variables and Data Types

To write basic Javascript programs, you need to understand the concept of variable and data types. Variables store data, like numbers or text strings, which can be used anywhere in your program. Data types determine how information is stored, and include numbers, strings, booleans (true/false values), objects, and arrays.

When declaring variables, you first use the keyword “var” followed by the name of the variable. You can then assign a value to it using an equal sign. To declare multiple variables at once, you can use comma-separated values. However, if you declare a variable without assigning a value, it will be assigned the value of “undefined”.

It is important to note that variables are case sensitive, so the variable “name” is not the same as the variable “Name”. Additionally, variables can be reassigned at any time, so you can change the value of a variable as your program runs. This is useful for keeping track of changing values, such as a user’s score in a game.

Working with Operators and Expressions

Javascript also includes logical operators that allow you to combine simple statements into complex expressions. Operators include equality (‘==’), comparison (‘<’), and arithmetic (‘+’). Expressions are used for comparing values and for assigning values to variables.

For instance, the expression ‘a > b’ evaluates to ‘true’ if a is greater than b. Similarly, the expression ‘firstName = “John”’ assigns the value “John” to the variable firstName.

In addition, logical operators can be used to combine multiple expressions into a single statement. For example, the expression ‘a > b && c < d’ evaluates to ‘true’ if both ‘a > b’ and ‘c < d’ are true. This allows you to create complex conditions that can be used to control the flow of your program.

Crafting Conditional Statements

Conditional statements are instructions that evaluate a statement as true or false. If the statement evaluates to true, one set of instructions will be executed; if it evaluates to false, another set of instructions will be executed. The “if…else” conditional statement is one of the most common used in programming. It takes two sets of instructions–one if the statement is true and another if it is false–and executes them accordingly. The “if…else if…else” statement is another type of conditional statement that allows for multiple conditions to be evaluated. This statement allows for multiple sets of instructions to be executed depending on the outcome of the evaluation. This type of statement is useful when there are multiple conditions that need to be evaluated and multiple sets of instructions that need to be executed.

Writing Functions and Loops

Functions are reusable code snippets that allow developers to write code more efficiently. They can be defined once, but reused multiple times in a program. Functions typically have parameters, which are placeholders for custom values. This allows you to quickly customize a program for different data sets.

Loops allow you to execute code multiple times with minimal effort. The two main loop types are ‘for’ and ‘while’. The ‘for’ loop executes a block of code until a certain condition is met, while the ‘while’ loop executes code until a certain condition stops being true.

Exploring the Document Object Model (DOM)

The Document Object Model (DOM) is an API used for interacting with HTML documents in a web browser. It enables developers to manipulate the content of an HTML document by adding, removing and changing existing elements. The DOM also exposes JavaScript events that can be used for creating interactive web pages.

Interacting with the Browser using Events

JavaScript events are triggered by user interactions with a webpage such as clicks, keystrokes and mouse movements. Events are handled by event handlers which can be used to execute code when an event occurs. For instance, if you want something to happen when the user clicks on a link, you can attach an onclick event handler to it.

Working with Timers and Asynchronous Processing

Timers can be used to execute code at specific intervals. The setInterval() method runs a specified piece of code at regular intervals, while setTimeout() executes code after a certain period of time has elapsed. Asynchronous programming is used for performing complex tasks without slowing down the browser, enabling web applications to respond quickly to user input even when processing large amounts of data.

Debugging Your Code

Once you have written some code, debugging it is important for making sure it works correctly. Debugging involves running your code in a testing environment and analyzing any errors that occur. Common mistakes include typos and incorrect variable names. Debugging tools like Chrome DevTools and Firebug can help you find and identify errors in your code.

Introducing Advanced Topics

Once you’ve grasped the basics of Javascript programming, there are a number of advanced topics you can explore. Learning how to use the jQuery library enables developers to create interactive web pages with minimal effort. You could also learn how to integrate third-party APIs into your web server or develop mobile applications with PhoneGap.

Conclusion

Javascript is an essential language for modern web development. While it takes some time to master all its concepts, it gets easier as you practice more. With some dedication and experimentation, you’ll soon be able to create complex web applications using Javascript.

Anand Das

Anand Das

Anand is Co-founder and CTO of Bito. He leads technical strategy and engineering, and is our biggest user! Formerly, Anand was CTO of Eyeota, a data company acquired by Dun & Bradstreet. He is co-founder of PubMatic, where he led the building of an ad exchange system that handles over 1 Trillion bids per day.

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