Starting today, we will start learning JavaSCript. Although I have been exposed to JavaScript before, I am writing conceptual and some simple js code pages, but I have not studied it systematically. I just search for the effect directly from the Internet and get it into my own project. Abnormal, then it is over, so that even though we have been in contact for several years now, it is still in a vague state.
Since you want to learn JavaScript systematically, let's first figure out what JavaScript is. In fact, many times the concept is not important, because no one will ask you what is JavaScript, what is JavaScript, when was it developed, who invented it, why invented it, etc. But since it is necessary to study systematically, these concepts do not need to be memorized according to the official definition, but it is still necessary to have an understanding. Because some concepts have multiple names, that is, multiple names and different names, just like some people call JavaScript js, some people call it a scripting language, and some people call it ECMAScript.
Now JavaScript is often abbreviated as js, and js and ECMAScript are often expressed with the same meaning, but js means more than what is specified in ECMAScript. A complete js implementation consists of three parts: the core (ECMAScript), the document object model (DOM), and the browser object model (BOM), as shown in the following figure:
It can be seen that the js and ECMAript we usually talk about are the core of js, and they are not completely equivalent. To clarify the concept, recognize the similarities and differences between js and ECMAript, this is the main purpose of this blog. For a detailed overview of ECMAScript, you can refer to Baidu or read related books, so I won't go into details.