دانلود کتاب شروع jQuery – از اصول jQuery تا نوشتن پلاگین‌های خود

jQuery is a framework that’s built on top of JavaScript, not a language in its own right. It is possible to write jQuery with barely any knowledge of JavaScript, but it’s not something we would recommend. If you want to be able to confidently write jQuery plug-ins for your site, or alter plug-ins others have written, you need to be familiar with basic JavaScript. That is why this book starts with JavaScript that you need to know. This chapter covers • JavaScript scripts on a web page • Variables and objects in JavaScript • JavaScript functions • Conditionals • Looping over arrays and objects • Debugging JavaScript If you are familiar with JavaScript, you might feel like skipping this chapter. That’s fine, but please consider skimming it first to ensure that you are comfortable with everything covered. Resist the temptation to skip to the jQuery parts—because you will struggle with it. Trust us, in a couple of chapters’ time, this preparation will all seem worth it. Many developers we’ve helped online have dived into jQuery eagerly before quickly becoming stuck due to a lack of understanding the language jQuery is built on. When you’re writing jQuery, you’re writing JavaScript, but using the jQuery library. We cannot stress how important it is that you make sure you are comfortable with the content covered in this chapter before moving on. We suggest that you try out the code as you read through this chapter. Don’t fool yourself into thinking you understand it because you’ve read it; there is no substitute for typing out the code yourself. To run the code, we recommend using JS Console (https://jsconsole.com), a tool by Remy Sharp that allows you to execute JavaScript and see the results. Some alternatives are JS Bin (http://jsbin.com) or JSFiddle (https://jsfiddle.net). You can enter the code in the browser and see the results. This is really useful for short lines of code. Figure 1-1 shows an example of JS Console.