


Comparison of several different ways of writing js self-executing functions_javascript skills
It is often necessary for a function to execute itself, but unfortunately this way of writing is wrong:
function(){alert(1);}();
The reason is that the first half of "function(){alert(1);}" is regarded as a function declaration instead of A function expression, which makes the following "();" become isolated and cause a syntax error.
According to the above analysis, although this piece of code has no grammatical errors, it does not meet our expectations because this function does not execute itself.
function(){alert(1);}(1 );
To sum up, the crux is how to make it clear that the code describes a function expression rather than a function declaration statement.
There are many correct ways to write, each with its own pros and cons:
Method 1: Add brackets first and last
(function(){alert(1);}());
This is the writing method recommended by jslint. The advantage is that it reminds people who read the code that this code is a whole.
For example, in an editor with a syntax highlighting matching function, when the cursor is behind the first left bracket, the last right bracket will also be highlighted, and people looking at the code can see the whole thing at a glance.
However, for some students who don’t like to add semicolons after lines when writing code, there will also be some pitfalls. For example, the following code will report a run error:
var a=1
(function(){alert(1);}());
Method 2: Add brackets around the function
(function(){alert(1);})();
This approach has one less code integrity benefit than method 1.
Method 3: Add operator before function, the common ones are ! and void.
!function(){alert(1);}( );
void function(){alert(2);}();
Obviously, adding operators such as "!" or " " is the simplest to write of.
It takes five keystrokes to add "void", but I heard that one advantage is that it requires one less logical operation than adding "!". ----I just heard about it, I don’t know why.
Finally, on my personal behalf, I strongly support method 1, which is the recommended way of writing jslint:
(function(){alert(1);}());

JavaScript runs in browsers and Node.js environments and relies on the JavaScript engine to parse and execute code. 1) Generate abstract syntax tree (AST) in the parsing stage; 2) convert AST into bytecode or machine code in the compilation stage; 3) execute the compiled code in the execution stage.

The future trends of Python and JavaScript include: 1. Python will consolidate its position in the fields of scientific computing and AI, 2. JavaScript will promote the development of web technology, 3. Cross-platform development will become a hot topic, and 4. Performance optimization will be the focus. Both will continue to expand application scenarios in their respective fields and make more breakthroughs in performance.

Both Python and JavaScript's choices in development environments are important. 1) Python's development environment includes PyCharm, JupyterNotebook and Anaconda, which are suitable for data science and rapid prototyping. 2) The development environment of JavaScript includes Node.js, VSCode and Webpack, which are suitable for front-end and back-end development. Choosing the right tools according to project needs can improve development efficiency and project success rate.

Yes, the engine core of JavaScript is written in C. 1) The C language provides efficient performance and underlying control, which is suitable for the development of JavaScript engine. 2) Taking the V8 engine as an example, its core is written in C, combining the efficiency and object-oriented characteristics of C. 3) The working principle of the JavaScript engine includes parsing, compiling and execution, and the C language plays a key role in these processes.

JavaScript is at the heart of modern websites because it enhances the interactivity and dynamicity of web pages. 1) It allows to change content without refreshing the page, 2) manipulate web pages through DOMAPI, 3) support complex interactive effects such as animation and drag-and-drop, 4) optimize performance and best practices to improve user experience.

C and JavaScript achieve interoperability through WebAssembly. 1) C code is compiled into WebAssembly module and introduced into JavaScript environment to enhance computing power. 2) In game development, C handles physics engines and graphics rendering, and JavaScript is responsible for game logic and user interface.

JavaScript is widely used in websites, mobile applications, desktop applications and server-side programming. 1) In website development, JavaScript operates DOM together with HTML and CSS to achieve dynamic effects and supports frameworks such as jQuery and React. 2) Through ReactNative and Ionic, JavaScript is used to develop cross-platform mobile applications. 3) The Electron framework enables JavaScript to build desktop applications. 4) Node.js allows JavaScript to run on the server side and supports high concurrent requests.

Python is more suitable for data science and automation, while JavaScript is more suitable for front-end and full-stack development. 1. Python performs well in data science and machine learning, using libraries such as NumPy and Pandas for data processing and modeling. 2. Python is concise and efficient in automation and scripting. 3. JavaScript is indispensable in front-end development and is used to build dynamic web pages and single-page applications. 4. JavaScript plays a role in back-end development through Node.js and supports full-stack development.


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