Solutions you can use to debug JavaScript errors_javascript tips
A Use the alert() and document.write() methods to monitor variable values
If you want to interrupt the running of the code and monitor the value of the variable, use the alert() method;
If there are many values that need to be viewed, use document .write() method to avoid repeatedly clicking the "OK" button;
B Use the window.onerror event
When an exception occurs on the page, the onerror event will be triggered on the window object. It can tell developers relevant error information to a certain extent.
Example:
Note: In IE, after the error event is triggered, the normal code will continue to run, and all variables and data will be saved and can be accessed normally in its onerror event handling method; in Firefox, after the error event is triggered, everything is over and all variables and data will be destroyed.
C Use try...catch statement to find errors
Example:
Note: try...catch does not handle JavaScript syntax well mistake.
Example:
This example does not enter the catch block.
D Use relevant debuggers
In IE and Firefox browsers, you can use relevant debuggers or plug-ins to debug JavaScript.
● In Firefox browser, you can use its own "error console". The steps are as follows:
Open the Firefox browser → go to "Tools" in the menu bar → select "Error Console".
In the absence of other plug-ins, its built-in "error console" is a very good choice.
In addition, in the Firefox browser, there are some very good debuggers, such as: Venkman, Firebug, etc.
After the Venkman debugger is installed, it can be enabled in the Firefox browser → in the menu bar "Tools" → select the "JavaScript Debugger" command;
After the Firebug debugger is installed, it can be enabled in the Firefox browser → in the menu bar " "Tools" → Select "Firebug" → Select "Open Firebug";
● In IE browser, you can use the Microsoft Script Debugger debugger
Microsoft Script Debugger is released with IE 4 by Microsoft An IE plug-in can be downloaded for free from Microsoft's official website.
After downloading and installing, the debugging option of the IE browser must be turned on before it can be used. The steps are as follows:
1> Open the IE browser → Select "Tools" on the menu bar → "Internet Options" command → "Advanced" tab → Check the "Disable script debugging (Internet Explorer)" check box Just remove it.
2> When the IE browser is browsing the page, run the Microsoft Script Debugger debugger tool to debug.
Select the open page file (read-only) in the Running Document panel of the Microsoft Script Debugger debugger, and then press F9 to set breakpoint debugging. In addition, its Command Window panel is also a very useful function. When the code stops at a breakpoint, you can enter the variable name and press Enter to see the value of the variable at that time; the Command Window panel can even accept simple JavaScript Order. But the Microsoft Script Debugger debugger itself still has a bug problem.

JavaScript originated in 1995 and was created by Brandon Ike, and realized the language into C. 1.C language provides high performance and system-level programming capabilities for JavaScript. 2. JavaScript's memory management and performance optimization rely on C language. 3. The cross-platform feature of C language helps JavaScript run efficiently on different operating systems.

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.


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