JavaScript alert, prompt, and confirm

alert

The alert function accepts a single argument. It displays the result on a modal dialog window.

The word "modal" means a user can't interact with the rest of the page.

The modal dialog window is a small box displayed on a web page.

Syntax:

alert(arg);

alert('Hello World!');

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prompt

The prompt function accepts two arguments.

Syntax:

prompt(arg1[, arg2]);

• arg1 is required.
• arg2 is optional.

On Internet Explorer, arg2 is required.

// For other browsers
const birthYear = prompt("What year were you born?");
alert(birthYear);

// For Internet Explorer
const yourName = prompt("What is your name?", "Michelle");
alert(yourName); 

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confirm

The confirm function only accepts an argument.

Syntax:

confirm(arg);

If OK is clicked, the result is true and false otherwise.

const isDoctor = confirm("Are you a Doctor?");
alert(isDoctor); // true if OK button is clicked

The above example is the same as below:

const isDoctor = prompt("Are you a Doctor?");
// const isDoctor = prompt("Are you a Doctor?", 'y/n'); IE

if (isDoctor === 'y') {
  alert("true");
} else if (isDoctor === 'n') {
  alert("false");
} else {
  alert("enter either y/n")
}  

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