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Introduction to JavaScript

Let's understand what is JavaScript?

  • JavaScript is a scripting or programming language that allows you to implement complex features on web pages.

  • JavaScript is HIGH-LEVEL Object- oriented programming, Multi-Paradigm programming language.

Getting Started with Hello World​

Hello world is very basic program to start with: 

console.log("Hello World!");

How many ways JavaScript can be added in browser??​

Using Script tag in HTML

  • In html file you can use <script></script> tag and under that write Javascript code.

=> Let's see an example:

<!DOCTYPE html>
<html>
<head>
<script>
function myFunction() {
  document.getElementById("demo").innerHTML = "Paragraph changed.";
}
</script>
</head>
<body>
<h2>Demo JavaScript in Head</h2>

<p id="demo">A Paragraph</p>
<button type="button" onclick="myFunction()">Try it</button>

</body>
</html>

Individual .js file

  • JavaScript can be added with <script> </script> tag.
  • Javascript should be linked at last of line as code works line by line and first html css will be loaded and then script will be loaded.
  • src attribute is used for giving source of file i.e what is file name and which location.

=> Suppose file is named as index.html:

<!-- Html File -->
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Javascript file added</title>
</head>
<body>
      <p> JavaScript Loaded </p>

      <script src="./app.js"></script>
</body>
</html>

JavaScript File is: 

// app.js file
document.write("Hello I am Nishtha!!");

Output

It will print: 
    JavaScript Loaded
    Hello I am Nishtha!!