#   
## 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

Use the JavaScript `<script>` tag in the head or body of an HTML file for interactivity.