15.6 JS Popup Alert

Confirm Box

• A confirm box is often used if you want the user to verify or accept something.
• When a confirm box pops up, the user will have to click either "OK" or "Cancel" to proceed.
• If the user clicks "OK", the box returns true. If the user clicks "Cancel", the box returns false.

Syntax

window.confirm("sometext");

The window.confirm() method can be written without the window prefix.

Example 2: JS Alert - Confirm Box

if (confirm("Press a button!")) {
  txt = "You pressed OK!";
} else {
  txt = "You pressed Cancel!";
}

Prompt Box

• A prompt box is often used if you want the user to input a value before entering a page.
• When a prompt box pops up, the user will have to click either "OK" or "Cancel" to proceed after entering an input value.
• If the user clicks "OK" the box returns the input value. If the user clicks "Cancel" the box returns null.

Syntax

window.prompt("sometext","defaultText");

The window.prompt() method can be written without the window prefix.

Example 3: JS Alert - Prompt Box

var person = prompt("Please enter your name", "Harry Potter");

if (person == null || person == "") {
  txt = "User cancelled the prompt.";
} else {
  txt = "Hello " + person + "! How are you today?";
}

Line Breaks

To display line breaks inside a popup box, use a back-slash followed by the character n.

Example 4: JS Alert - Line Breaks

alert("Hello\nHow are you?");