JavaScript data type verification method_javascript skills
Recently, I have a new understanding of the verification of JavaScript data types. It turns out that it can be so simple and so comprehensive.
We have customized isString, isNumber, isDate, isError, isRegExp, isBoolean, isNull, isUndefined, isObject and other methods. Now show the javascript data type verification function and test set you defined:
<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title></title> </head> <body> </body> <script type="text/javascript"> //isString //isNumber //isDate //isError //isRegExp //直接利用和数据类型来判断 [].forEach.call(['String','Number','Date','Error','RegExp'],function(name){ this['is'+name]=function(obj){ return toString.call(obj)==='[object '+name+']'; }; }); //isBoolean //true和false需要考虑在内 Object.prototype.isBoolean=function(obj){ return obj===true||obj===false||toString.call(obj)==='[object Boolean]'; }; //isNull //未找到所指向对象 Object.prototype.isNull=function(obj){ return obj===null; }; //isUndefined //定义了但是未赋值 Object.prototype.isUndefined=function(obj){ return obj===void 0; }; //isObject //函数和数组都是对象 Object.prototype.isObject=function(obj){ var type = typeof obj; return type === 'function' || type === 'object' && !!obj; }; //test //isString var str="iamstring"; var a=isString(str); console.log(a);//true //isNumber var b=isNumber(a); console.log(b);//false //isNumber var num=4; var c=isNumber(num); console.log(c);//true //isRegExp var reg=/^[1-9]/; var d=isRegExp(reg); console.log(d);//true //isDate var date=new Date(); var e=isDate(date); console.log(e);//true //isBoolean var bool=false; var f=isBoolean(bool); console.log(f);//true //isNull var nul=document.getElementById("div02"); var g=isNull(nul); console.log(g);//true //isUndefined var undef; var h=isUndefined(undef); console.log(h);//true //isObject var obj={"1":"1","2":"2"}; var i=isObject(obj); console.log(i);//true </script> </html>
The following is a detailed introduction to judging the data type of JavaScript, which is divided into six data types. Friends in need can come and refer to it. I hope it will be helpful to everyone
1. Determine whether it is an array type
The code is as follows:
<STRONG><script type="text/javascript"> //<![CDATA[ var a=[0]; document.write(isArray(a),'<br/>'); function isArray(obj){ return (typeof obj=='object')&&obj.constructor==Array; } //]]> </script></STRONG>
2 Determine whether it is a string type
The code is as follows:
<script type="text/javascript"> //<![CDATA[ document.write(isString('test'),'<br/>'); document.write(isString(10),'<br/>'); function isString(str){ return (typeof str=='string')&&str.constructor==String; } //]]> </script>
3 Determine whether it is a numeric type
The code is as follows:
<script type="text/javascript"> //<![CDATA[ document.write(isNumber('test'),'<br/>'); document.write(isNumber(10),'<br/>'); function isNumber(obj){ return (typeof obj=='number')&&obj.constructor==Number; } //]]> </script>
4 Determine whether it is date type
The code is as follows:
<script type="text/javascript"> //<![CDATA[ document.write(isDate(new Date()),'<br/>'); document.write(isDate(10),'<br/>'); function isDate(obj){ return (typeof obj=='object')&&obj.constructor==Date; } //]]> </script>
5 Determine whether it is a function
The code is as follows:
<script type="text/javascript"> //<![CDATA[ document.write(isFunction(function test(){}),'<br/>'); document.write(isFunction(10),'<br/>'); function isFunction(obj){ return (typeof obj=='function')&&obj.constructor==Function; } //]]> </script>
6 Determine whether it is an object
The code is as follows:
<script type="text/javascript"> linenum //<![CDATA[ document.write(isObject(new Object()),'<br/>'); document.write(isObject(10),'<br/>'); function isObject(obj){ return (typeof obj=='object')&&obj.constructor==Object; } //]]> </script>
I hope this article will be helpful to everyone learning JavaScript programming.

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.

C and C play a vital role in the JavaScript engine, mainly used to implement interpreters and JIT compilers. 1) C is used to parse JavaScript source code and generate an abstract syntax tree. 2) C is responsible for generating and executing bytecode. 3) C implements the JIT compiler, optimizes and compiles hot-spot code at runtime, and significantly improves the execution efficiency of JavaScript.


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