JavaScript Course | Interaction With User

Last Updated : 29 Apr, 2019

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Javascript allows us the privilege with which we can interact with the user and respond accordingly. It includes several user-interface functions which help in the interaction. Let’s take a look at them one by one.

alert
simply creates an alert box which may or may not have specified content inside it, but it always comes with the ‘OK’ button. It simply shows a message and pauses the execution of the script until you press the ‘OK’ button. The mini-window that pops-up is called the ‘modal window’.
```
alert('text');
```
Example:

// alert example
<script>
alert('HI there'); // with specified content
alert(); // without any specified content
</script>
Output:

It can be used for debugging or simply for popping something to the user.
prompt
Prompt is another user-interface function which normally contains two arguments.
```
prompt('text', default value);
```
The text is basically what you want to show the user and the default value argument is optional though it acts like a placeholder inside a text field. It is the most used interface as with it you can ask the user to input something and then use that input to build something.
Example:(with default parameter)

<script>
// prompt example
let age = prompt('How old are you?', 50);

alert(`You are ${age} years old!`);
</script>
Output:

You can enter anything and it will print that, it doesn’t necessarily have to be a number. Without the default value, you have to enter something in the text-field otherwise it will print a blank space simply.
Example:

<script>
// prompt example
let age = prompt('How old are you?');

alert(`You are ${age} years old!`);
</script>
Output:
confirm
The confirm function basically outputs a modal window with a question and two button ‘OK’ and ‘CANCEL’.
```
confirm('question');
```
Example:

<script>
// confirm example
let isHappy = confirm('Are you Happy?');
alert(`You are ${isHappy}`);
</script>
Output:

It will print true or false based on your choice of clicking the ‘OK’ button or ‘CANCEL’ button respectively.