Coding with JavaScript For Dummies
Overview
Go from beginner to builder quickly with this hands-on JavaScript guide
Coding with JavaScript For Dummies provides easy, hands-on instruction for anyone looking to learn this popular client-side language. No experience? No problem! This friendly guide starts from the very beginning and walks you through the basics, then shows you how to apply what you've learned to real projects. You'll start building right away, including web page elements and simple applications, so you can immediately see how JavaScript is used in the real world. Online exercises allow you to test your code and expand your skills, and the easy-to-follow instruction provides step-by-step guidance toward understanding the JavaScript syntax, applications, and language.
JavaScript enhances static web pages by providing dynamic elements that can adapt and react to user action. It's a need-to-know tool for aspiring web
designers, but anyone can benefit from understanding this core development language. Coding with JavaScript For Dummies takes you from beginner to builder quickly as you:
- Learn what JavaScript does, how it works, and where to use it
- Master the core elements of JavaScript and immediately put it to work
- Build interactive web elements and try out your code online
- Create basic applications as you apply JavaScript to the app development workflow
Anytime a website responds to your movement around the screen, that's JavaScript. It makes websites more functional, more beautiful, and more engaging, and your site visitors will demand nothing less. If you want to build a better website, you need JavaScript. If you need JavaScript, Coding with JavaScript For Dummies gets you started off quickly and painlessly, with plenty of hands-on practice.
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About The Author
Chris Minnick is an accomplished author, trainer, and web developer who has worked on web and mobile projects for both small and major businesses. Eva Holland is an experienced writer and trainer who has designed and taught online, in-person, and video courses. They are cofounders of WatzThis?
Sample Chapters
coding with javascript for dummies
CHEAT SHEET
JavaScript opens up Web pages to you so that you can add interactive features and those user-friendly touches. Of course, you have to know how to fit JavaScript into existing code and what to input to get the effects you want. And, when things aren't working well, you may need a little help troubleshooting the problem to get back on track.
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JavaScript
Even the best JavaScript programmers make mistakes. Sometimes, these mistakes cause your program to not produce the results that you wanted, and sometimes they cause the program to not run at all. Here are ten common mistakes that JavaScript programmers at all levels often make.
Equality confusion
Does x equal y?
JavaScript
You’ve only just begun your JavaScript journey. The universe of tools, frameworks, and libraries built with JavaScript and that will help you write better JavaScript programs is vast and growing at a mind-boggling pace. Here are ten great JavaScript frameworks and libraries.Angular JSAngular JS.
Angular JS, commonly referred to as Angular, is an open source JavaScript application framework.
JavaScript
JavaScript has more libraries, resources, and helpful tools for working with it than for any other programming language. Here are ten of the best resources for helping you write more and better JavaScript.JSLintJSLint shows you where your code has problems.
JSLint, created by JavaScript super-genius Douglas Crockford, is a code checker that is designed to tell you where your code has problems — and not just the kind of problems that would generate errors.
JavaScript
JavaScript has more to it than meets the eye. As you begin programming, you wull discover just howversatile it is. Here are ten things that JavaScript can do that you may not have known about:
Make better TV: The Yahoo! ConnectedTV platform allows programmers to write TV apps using JavaScript. Apps built with Yahoo!
JavaScript
Understanding arrays is an important part of coding with JavaScript. An array consists of array elements. Array elements are made up of the array name and then an index number that is contained in square brackets. The individual value within an array is called an array element. Arrays use numbers (called the index numbers) to access those elements.
JavaScript
Master coding with JavaScript by discovering which words are reserved in JavaScript, an extensive list of HTML5 APIs, and jQuery selectors. Just check out these helpful tips to get started.JavaScript reserved wordsWhen coding with JavaScript, it will benefit you to know certain reserved words. The following list contains JavaScript reserved words.
JavaScript
Coding with JavaScript is made easier with the use of regular expressions. Regular expressions are used with the regular expression methods and with a subset of the string functions. The regular expression methods are
test: Tests for a match and returns true if a match is found and false if none is found.
exec: Tests for a match and returns an array of information about the match.
One major cause of slow web pages is the so-called blocking script. A blocking script is a JavaScript file whose loading and execution blocks the loading of a web page. In extreme circumstances, a browser may download an entire webpage and show a blank screen for several seconds or longer while the JavaScript is loaded and parsed.
JavaScript
In JavaScript, the getElementBy methods provide easy access to any element or groups of elements in a document without relying on parent/child relationships of nodes. The three most commonly used ways to access elements are
getElementById
getElementsByTagName
getElementsByClassName
getElementById
By far the most widely used method for selecting elements, getElementById is essential to modern web development.
JavaScript
How do you access audio and video when coding with JavaScript? Prior to HTML5, the only way for a web page to use a camera connected to a computer or built into a computer was through the use of plugins, such as Flash.
One of the major goals of HTML5 is to eliminate the need for plugins, with their constant updates and security issues.
JavaScript
One of the most common things that JavaScript programmers need to do with geolocation data is to display a location on a map. In order to do this, you first need to get the latitude and longitude. You’ve got that now. But, how do you draw the map and figure out where on the map that latitude and longitude are?
JavaScript has a data type called object. JavaScript objects encapsulate data and functionality in reusable components. You may find that creating an object is the next logical step in your coding journey.
JavaScript has two ways to create objects:
By writing an object literal
By using the object constructor method
Which one you choose depends on the circumstances.
JavaScript
In order for JavaScript functions to be able to do the same thing with different input, they need a way for programmers to give them input. The difference between parameters and arguments can be confusing at first. Here’s how it works:
Parameters are the names you specify in the function definition.
Arguments are the values you pass to the function.
JavaScript
You may want to use JSON with your JavaScript code to put objects in motion. In this example, you use AJAX to open and display a text document containing a snippet of HTML. Another common use for AJAX is to request and receive data for processing by the browser. For example, gasbuddy.com uses a map from Google along with data about gas prices, to present a simple and up-to-date view of gas prices in different locations.
JavaScript
After you create an object and define its properties in JavaScript, you’ll want to be able to retrieve and change those properties. The two ways to access object properties are by using dot notation or square brackets notation.
Dot notation
In dot notation, the name of an object is followed by a period (or dot), followed by the name of the property that you want to get or set.
JavaScript
The function name part of the function head isn’t required in JavaScript, and you can create functions without names. This may seem like an odd thing to do because a function with no name is like a dog with no name; you have no way to call it! However, anonymous functions can be assigned to variables when they are created, which gives you the same capabilities as using a name within the function head:
var doTheThing = function(thingToDo) {
document.
A closure is like keeping a copy of the local variables of a JavaScript function as they were when the closure was created. In web programming, closures are frequently used to eliminate the duplication of effort within a program or to hold values that need to be reused throughout a program so that the program doesn’t need to recalculate the value each time it’s used.
JavaScript
In JavaScript, the properties of the Form object match up with the attributes of the HTML form element. They’re used for getting or setting the values of the HTML form element attributes with JavaScript. Check out the list of all the properties of the Form object.
DOM objects are representations of HTML pages.
JavaScript
JavaScript code writers need to have a form grasp on geolocation. The Geolocation API gives programs access to the web browser’s geolocation functionality, which can tell the program the device’s location on Earth. The Geolocation API is among the most well-supported HTML5 APIs and is implemented in about 90 percent of desktop and mobile browsers, including all of the big ones, except for Opera Mini.
The HTML script element allows you to embed JavaScript into an HTML document. Often script elements are placed within the head element, and, in fact, this placement was often stated as a requirement. Today, however, script elements are used within the head element as well as in the body of web pages.
The format of the script element is very simple:
<script>
(insert your JavaScript here)
</script>
Here’s an example of an HTML document with a script tag containing JavaScript.
You can call functions from outside of the function or from within other functions with JavaScript. You can even call a function from within itself. When a function calls itself, it’s using a programming technique called recursion.
You can use recursion in many of the same cases where you would use a loop, except that it repeats the statements within a function.
JavaScript
The engines that make expressions do their work are called operators. They operate on data to produce different results. JavaScript’s special operators are a hodge-podge of miscellaneous other symbols and words that perform other and important functions.
Conditional operator
The conditional operator (also known as the ternary operator) uses three operands.
JavaScript
In JavaScript, the Attribute object provides properties for working with attributes within the HTML elements. Here is a list of all the Attribute object’s properties.
Property
Use
isId
Yields true if the attribute is an
Id; otherwise, yields false
name
Gets the name of the attribute
value
Gets or sets the value of the attribute
specified
Yields true if the attribute has been
specified; otherwise, yields false
Creating and appending elements
To create a new element in an HTML document, use the document.
Sometimes, it’s helpful to be able to run JavaScript commands without creating an HTML page and including separate scripts or creating blocks. For these times, you can use the Chrome browser’s JavaScript Console.
To access the JavaScript Console, find the Chrome menu in the upper-right corner of your browser.
Learning to write functions can make the life of a JavaScript programmer significantly easier. A function declaration must be written in a specific order. A function declaration consists of the following items, in this order:
Function keyword
Name of the function
Parentheses, which may contain one or more parameters
Pair of curly brackets containing statements
Sometimes, a function’s whole purpose will be to write a message to the screen in a web page.
JavaScript
Before you can make use of a regular expression in JavaScript, you need to create an object containing the expression. You can write regular expressions in one of two ways:
By using a regular expression literal
Through the constructor function of the RegExp object
Using the RegExp object
When you create a regular expression by calling the RegExp constructor function, the resulting object gets created at run time, rather than when the script is loaded.
JavaScript
The most popular way to include JavaScript in HTML documents is by using the src attribute of the script element. A script element with a src attribute works exactly like a script element with JavaScript between the tags, except that if you use the src attribute, the JavaScript is loaded into the HTML document from a separate file.
JavaScript opens up Web pages to you so that you can add interactive features and those user-friendly touches. Of course, you have to know how to fit JavaScript into existing code and what to input to get the effects you want. And, when things aren't working well, you may need a little help troubleshooting the problem to get back on track.
When coding with JavaScript, it will benefit you to know certain reserved words. The following list contains JavaScript reserved words. You can’t use these words as JavaScript variables, functions, methods, loop labels, or object names.
abstract
final
public
boolean
finally
return
break
float
short
byte
for
s
Strict mode is an optional way to force web browsers to run a restricted version of JavaScript. Strict mode treats mistakes in your code that are normally considered bad style as actual errors that will cause your programs to not run. Using strict mode makes your JavaScript code more secure and can even make your programs run faster.
JavaScript
Here is an extensive list of HTML5 APIs that have either been proposed or implemented. Browsers are constantly being updated with new features. For the latest on which browsers support which features, visit caniuse.com.
API
What It Does
Ambient Light API
Provides information about the ambient light levels, as
detected by a device’s light sensor.
JavaScript
Using functions to code with JavaScript can be very useful to a programmer. Here is a program that adds numbers together. It works great and does exactly what it’s supposed to do, using a for......in loop.
<html>
<head>
<title>Get the total</title>
</head>
<body>
<script>
var myNumbers = [2,4,2,7];
var total = 0;
for (oneNumber in myNumbers){
total = total + myNumbers[oneNumber];
}
document.
Underscore is a collection of more than 100 useful JavaScript functions to help you get started and be more productive with JavaScript. To use Underscore’s functions on a web page, you need to include it using the script element. You can either include the library within the head element or load it right before the closing body tag in order to avoid blocking the loading of your web page while Underscore is loading.
JavaScript
Not only can you store arrays inside of arrays with JavaScript, you can even put arrays inside of arrays inside of arrays. This can go on and on. An array that contains an array is called a multidimensional array. To write a multidimensional array, you simply add more sets of square brackets to a variable name.
HTML5 brings some pretty amazing new functionality to JavaScript web pages, and the HTML 5 APIs are rapidly giving web browsers access to new universes of data and making installable computer applications a thing of the past. However, not every browser is on board with the future yet. Or, not every browser can agree on what that future should be.
JavaScript functions are objects. This statement is the key to understanding many of the more advanced JavaScript topics, including callback functions. Functions, like any other object, can be assigned to variables, be passed as arguments to other functions, and created within and returned from functions.
Passing functions as arguments
A callback function is a function that is passed as an argument to another function.
JavaScript
When you create objects with JavaScript, you’re not just limited to creating specific objects, such as your guitar, your car, your cat, or your sandwich. The real beauty of objects is that you can use them to create types of objects, from which other objects can be created.
Here, a new person object of the type Object is created.
Methods are properties with functions for their values. In JavaScript, you define a method the same way that you define any function. The only difference is that a method is assigned to a property of an object. This example demonstrates the creation of an object with several properties, one of which is a method.
JavaScript
HTML DOM trees resemble family trees in the hierarchical relationship between nodes. In fact, the technical terms used by JavaScript programmers to describe relationships between nodes in a tree take their names from familial relationships.
Every node, except the root node, has one parent.
Each node may have any number of children.
JavaScript
In JavaScript, you can display node types and node values by using the HTML DOM. You also can set property values of elements within the DOM using the Element object. When you use JavaScript to set the properties of DOM elements, the new values are reflected in real-time within the HTML document.
Changing the properties of elements in a web document in order to reflect them instantly in the browser, without needing to refresh or reload the web page, is a cornerstone of what used to be called web 2.
JQuery provides many different ways to match sets of elements within a document beyond the methods built into JavaScript. Check out this list of all the jQuery selectors. To use them, simply pass them to the jQuery function (or, you can use the $ alias for the jQuery function). For example:
$("*") selects every element.
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