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Js For Beginners

Why Study JavaScript? JavaScript is one of the 3 languages all web developers must learn: 1. HTML to define the content of web pages 2. CSS to specify the layout of web pages 3. JavaScript to program the behavior of web pages

What is meant by js?
Javascript (JS) is a scripting languages, primarily used on the Web. It is used to enhance HTML pages and is commonly found embedded in HTML code. JavaScript is an interpreted language. JavaScript renders web pages in an interactive and dynamic fashion.

What is the use of JavaScript?

HTML Javascript-jsis a text-based programming language used both on the client-side and server-side that allows you to make web pages interactive. Where HTML and CSS are languages that give structure and style to web pages, JavaScript gives web pages interactive elements that engage a user.

Is JS good for beginners?

JavaScript is intuitive for a beginner just learning to code and a great vehicle to teach students the principles of Computer Science.Whether you're planning on eventually being a front-end or back-end developer, there's no doubt that JavaScript is the best coding language to learn for beginners.

Is JavaScript and Java same?

The JavaScript programming language, developed by Netscape, Inc., is not part of the Java platform.Java is an OOP programming language while Java Script is an OOP scripting language. Java creates applications that run in a virtual machine or browser while JavaScript code is run on a browser only.

Is Python better than JavaScript?Hands down, JavaScript is undeniably better than Python for website development for one simple reason: JS runs in the browser while Python is a backend server-side language.Between JQuery, Angular, and React, JavaScript provides virtually endless capabilities for web programming.

How To JavaScript?

How To JavaScript?

The tags. 


    
    <script>
        
        document.getElementById("demo").innerHTML = "My First JavaScript";
    </script>

JavaScript in <head > or <body >

You can place any number of scripts in an HTML document. Scripts can be placed in the <body>, or in the <head> section of an HTML page, or in both.

JavaScript in <head>


    <head>
    <title>The Title</title>
        <link rel="stylesheet" href="stylebyjimbowales.css" /> <!-- Imports Stylesheets -->
        <script>
        function myFunction() {
            document.getElementById("demo").innerHTML = "Paragraph changed.";
        }
        </script>
    </head>

JavaScript in <body>


    <head>
    <title>The Title</title>
        <link rel="stylesheet" href="stylebyjimbowales.css" /> <!-- Imports Stylesheets -->
      
    </head>
    <body>

<div>style="background-color:black;color:white;padding:20px;">
        <h2>London</h2>
        <p>London is the capital city of England. It is the most populous city 
        in the United Kingdom, with a metropolitan area of over 13 million 
        inhabitants.</p>
    </div>


    <script>
        function myFunction() {
          document.getElementById("demo").innerHTML = "Paragraph changed.";
        }
    </script>
    </body>

External JavaScript

External scripts are practical when the same code is used in many different web pages. JavaScript files have the file extension .js. To use an external script, put the name of the script file in the src (source) attribute of a <script> tag: 


    <script>
        function myFunction() {
          document.getElementById("demo").innerHTML = "Paragraph changed.";
        }
    </script>     
    

    <script src="myScript.js"> </script>

External JavaScript Advantages

Placing scripts in external files has some advantages:
It separates HTML and code It makes HTML and JavaScript easier to read and maintain Cached JavaScript files can speed up page loads To add several script files to one page - use several script tags: 


   <script src="myScript2.js"></script>
   <script src="myScript6.js"></script>

External References

An external script can be referenced in 3 different ways:
With a full URL (a full web address) With a file path (like /js/) Without any path This example uses a full URL to link to myScript.js: 


    <script src="https://www.w3schools.com/js/myScript.js" > </script>

JavaScript Variables

4 Ways to Declare a JavaScript Variable:
Using var, Using let, Using const, Using nothing

What are Variables?

Variables are containers for storing data (storing data values).
In this example, x, y, and z, are variables, declared with the var keyword: 


    var x = 5;
    var y = 6;
    var z = x + y;

From all the examples above, you can guess: x stores the value 5 y stores the value 6 z stores the value 11

When to Use JavaScript const?

If you want a general rule: always declare variables with const. If you think the value of the variable can change, use let. In this example, price1, price2, and total, are variables:


       
        const variableName = 634;
        console.log(variableName);

When to Use JavaScript Let ?

The let keyword was introduced in ES6 (2015). Variables defined with let cannot be Redeclared. Variables defined with let must be Declared before use. Variables defined with let have Block Scope.


    let myVariable = 76;
    console.log(myVariable);

    myVariable = 1000;
    console.log(myVariable);

When to Use JavaScript var?

Always declare JavaScript variables with var,let, orconst. The var keyword is used in all JavaScript code from 1995 to 2015. The let and const keywords were added to JavaScript in 2015. If you want your code to run in older browser, you must use var.


    variableName = 3764783;
    console.log(variableName);


    var outVariables = 2000;
    console.log(outVariables);

JavaScript Data Types

The Concept of Data Types; In programming, data types is an important concept. To be able to operate on variables, it is important to know something about the type. Without data types, a computer cannot safely solve this:


    let x = 16 + "Volvo";

JavaScript Numbers

JavaScript has only one type of numbers. Numbers can be written with, or without decimals:


        let myVariable = 76;
        console.log(myVariable);


        let x1 = 34.00;     // Written with decimals
        let x2 = 34;        // Written without decimals

Javascript String

A string (or a text string) is a series of characters like "John Doe". Strings are written with quotes. You can use single or double quotes:


        const stringVariable = "Coding-Stuff";
        console.log(stringVariable);

JavaScript Booleans

Booleans can only have two values: true or false.


        let booleanVariable = false;
        console.log(booleanVariable);

JavaScript Arrays

JavaScript arrays are written with square brackets. Array items are separated by commas. The following code declares (creates) an array called cars, containing three items (car names):


       const arrayVariable = [76, 'hello', "world", true];
        console.log(arrayVariable[2]);

Undefined

In JavaScript, a variable without a value, has the value undefined. The type is also undefined. 


      
    let undefinedVariable
    console.log(undefinedVariable);

    let undefinedVariables = undefined;
    console.log(undefinedVariables);

    undefinedVariable = 576;
    console.log(undefinedVariable);

Empty Values/Null

An empty value has nothing to do with undefined. An empty string has both a legal value and a type.


          
    let nullVariable = null;
    console.log(nullVariable);

JavaScript Objects

JavaScript objects are written with curly braces {}. Object properties are written as name:value pairs, separated by commas.


          
    const objVariable = {
        firstName: 'john',
        lastName: "doe",
        age: 21,
        values: true,
        hobby: 'coding',
        };
    console.log(objVariable.firstName, objVariable.age, objVariable.hobby);

BigInt-Datatype

What is BIGINT data type? The BIGINT data type can represent 63-bit integers and is compatible with all numeric data types. The BIGINT function returns a big integer representation of a number or a string representation of a number. The range of big integers is -9223372036854775808 to 9223372036854775807.


          
    const bigVariable = 476378648384537864785348374n;
    console.log(bigVariable);

Typeof

You can use the JavaScript typeof operator to find the type of a JavaScript variable. The typeof operator returns the type of a variable or an expression:


          
    console.log(typeof objVariable);
    console.log(typeof stringVariable);
    console.log(typeof arrayVariable);
    console.log(typeof bigVariable);

Post Tags Development Design Web

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