#   
## JavaScript in HTML
To add interactiveness to a web page, we use the JavaScript `<script></script>` tag and include it in the HTML file. 

The location of the JavaScript element in the HTML file can be either in the `head` or `body` tag

## Example
We can place the `<script></script>` tag in the `<head>` and` <body>` section of an HTML file, as shown in the image below:


However, if we run different functions, it is best to put the `<script></script>` tag in the body section before the `</body>` closing tag. This ensures that the webpage loads faster.

<html>
 <head>
 </head>
 <body>
    Hello World
    <script>
        alert("How are you?");
    </script>
  </body>
</html>

codemirror

# 
## External JavaScript file
We can place the JavaScript codes in another file with the `.js` extension.  The JavaScript file should then be linked with the `src` attribute. 

In the example below, we create files in the `src` folder with the `.js` extension:


To link the JavaScript file to the HTML file, we need to input the code `<script src="src/app.js"></script>` in the `</body>` section of our HTML file before the </body> closing tag. Let’s look at an example below: 

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

import React from 'react';
import { shallow, configure } from 'enzyme';
import Adapter from 'enzyme-adapter-react-16';

configure({ adapter: new Adapter() });

import HelloWorld from './app';

var TestResult = function() {
    this.succeeded = false;
    this.reason = "";
    this.input = "";
    this.expected_output = "";
    this.actual_output = "";
}

export const executeTests = function() {

  var results = [];

  result = new TestResult();
  result.input = 'HelloWorld Component';
  result.expected_output = "span containing text 'Hello World'"

  let wrapper = shallow(<HelloWorld />);

  // Call your Challenge function here.

  let type = wrapper.type();
  let testSuccessful = true;
  let failureReason;

  if (type !== 'span') {
    testSuccessful = false;
    failureReason = "You need to render exactly one span HTML element";
  } else if (wrapper.props().children != "Hello World") {
     testSuccessful = false;
     failureReason = "You have rendered wrong message in your span element";
  }

  result.actual_output = wrapper.html();

  if (testSuccessful) {
    result.succeeded = true;
    result.reason = "Succeeded"
  } else {
    result.succeeded = false;
    result.reason = failureReason;
  }

  results.push(result);

  return results;
}


html_js

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How to use JavaScript in an HTML document

 JavaScript in HTML To add interactiveness to a web page, we use the JavaScript  tag and include it in the HTML file. The location of the JavaScript element in the HTML file can be either in the head or body tag Example We can place the  tag in the  and  section of an HTML file, as shown in the image below: 