


How to determine whether two strings are equal in JavaScript_Basic knowledge
Convert all user input values to uppercase (or lowercase) first, and then compare:
var name = document.form1.txtUserName.value.toLowerCase(); if(name == "urname") { // statements go here. }
JavaScript has two equality operators. One is completely backward compatible, the standard "==". If the two operand types are inconsistent, it will automatically perform type conversion on the operand at some point. Consider the following assignment statement:
var strA = "i love you!"; var strB = new String("i love you!");
These two variables contain the same sequence of characters, but have different data types. The former is string and the latter is object. When using the "==" operator, JavaScript will try various evaluations to detect whether the two will be in the same sequence. equal in some cases. So the following expression evaluates to true: strA == strB.
The second operator is the "strict" "===", which is not so forgiving when evaluating and does not perform type conversion. So the expression strA === strB evaluates to false, although both variables hold the same value.
Sometimes the logic of the code requires you to determine whether two values are not equal. There are two options here: "!=" and strict "!==". Their relationship is similar to "==" and "===".
Discussion:
"==" and "!=" will try their best to find matching values when evaluating, but you may still want to perform an explicit type conversion before comparing to "help" them do their job. For example, if you want to determine whether a user's input value (string) is equal to a number, you can let "==" help you complete the type conversion:
if(document.form1.txtAge.value == someNumericVar) { ... }
You can also convert in advance:
if(parseInt(document.form1.txtAge.value) == someNumericVar) { ... }
If you are more accustomed to strongly typed programming languages (such as C#, Java, etc.), then you can continue your habit (type conversion) here, which will also enhance the readability of the program.
There is one thing you need to pay attention to, which is the computer’s regional settings. If you compare strings with "", then JavaScript compares them as Unicode, but obviously people browsing the web don't read the text as Unicode :) For example in Spanish, According to traditional sorting, "ch" will be sorted as a character between "c" and "d". localeCompare() provides a way to use the character collation of the default locale.
var strings; // 要排序的字符串数组,假设已经得到初始化 strings.sort(function(a,b) { return a.localeCompare(b) }); // 调用sort()方法进行排序

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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