Server Side JS
Imperative and structured
JS is made up almost entirely of objects - associative arrays enhanced by the use of prototypes. Properties and their values can be created, modified/deleted at runtime. Most of them are included in the inheritance chain and are listed using the for … in loop statement. JS has a small number of predefined objects like Functiony Date.
First class functions
First class functions have properties and methods like.call() and.bind(). A nested function is one that is defined within another that is created whenever the outer function is called. In addition, each forms a closure that is the result of evaluating a domain containing one or more dependent variables from another environment, including constants, local variables, and calling function arguments. The result of evaluating the specified closure is part of the object's internal state, even after the outer function has completed its actions.
Prototypes instead of classes
JS uses prototypes instead of classes to use inheritance. You can emulate many of the features provided by classes in object-oriented languages through prototypes.
Functions also behave like constructors. Prefixing the call with the new keyword creates a new prototype instance that inherits the properties and methods from the constructor, including the properties of Object. ECMAScript 5 introduces the Object.create method, which allows instantiation without the need to automatically inherit from Object. In earlier environments, the prototype may have been created as null. The prototype property of the constructor defines the object for the internal newly created prototype. New methods can be added by changing the object's prototype, as a constructor.
An indefinite number of parameters can be passed to it. It accesses them through parameters or the local arguments object. The variádica function can be created using the.apply() method. Unlike many object-oriented languages, there is no distinction between a function definition and a method definition. Rather, it occurs during a function call that can be executed as a method with the this keyword, which is a local variable for the object that called the function.
The two languages share much of the same syntax, structure, establishing a hierarchy of objects to define their properties, and other elements that have much in common with C and C++.
Include language in XHTML documents
- This method is used when defining a small block of code or when you want to include specific default instructions in a website's HTML document. The main disadvantage is that ifyou need to make changes to the code block, you need to change all the pages that contain it. The complexity of the method requires developers to familiarize themselves with programming lessons from scratch.
In addition to the type attribute, the second method requires the introduction of a src attribute that specifies the URL corresponding to the JS file. Each tag can only link to one file, but you can include as many tags as needed on the same page.
JS type files are plain text documents with a.js extension that can be created with any text editor such as Notepad, Wordpad, EmEditor and UltraEdit.
This last method is less used because it includes JS snippets in the page's XHTML code. The main disadvantage of this method is that XHTML unnecessarily complicates JS serving. In general, this method is only used to detect some events.
Some browsers don't have full JS support, others allow partial blocking. There are users who also completely block JS because they consider it dangerous.
In these cases, if the web page requires JS to function, a warning message will appear indicating that theJS.
HTML defines a tag to display a message to the user when their browser cannot execute JS.
Possibilities and limitations
From the beginning, JS has always been widely used by most internet sites. The advent of Flash reduced its popularity as it allowed actions that JS could not.
Thus, JS scripts cannot interact with resources outside of the domain from which the script was loaded. Scripts cannot close windows that were not opened, and created windows cannot be too small or too large and placed out of the user's view.
In addition, scripts cannot access files on the computer in either read or write mode and cannot read or change browser settings. Finally, if the script takes a long time to complete, such as due to a programming error, the browser informs the user that the script is consuming a lot of resources and gives the option to stop execution.
The most modern browsers available include support for JS up to the third edition of the ECMA-262 standard. The unprecedented popularity of JS as a web application programming language has been extended to other applications andnon-network environments. Tools like Adobe Acrobat allow you to include JS code in PDF files. Other Adobe tools such as Flash and Flex use ActionScript, a dialect of the same JS standard. Photoshop allows you to create small scripts through JS, and version 6 of Java includes a new package (named javax.script) that allows you to integrate both languages.
Internet Explorer 8/9:
- Open an Internet Explorer browser window.
- Click on Tools in the top menu bar and select Internet Options or the Alt key.
- Select the "Security" tab.
- Click on the User level button.
- Scroll through the list of options until the script name appears.
- Set Enable Scripts to On.
- Press "OK" on each of the following two screens to confirm the change.
Firefox Browser 3.6+:
- Open the Firefox browser window.
- Click on Tools in the top menu bar and select "Options".
- Select the content icon at the top of the window that appears.
- Press "OK" to confirm the change.
- Click on the key icon on the browser toolbar.
- Select options.
- Click on the Advanced tab.
- Click on Content Settings under "Privacy".
- Click on JS.
- Select "Allow all sites to execute JS" (recommended).
- Click Close.