JavaScript
Popup Boxes
JavaScript
has three kind of popup boxes: Alert box, Confirm box, and Prompt box.
Alert
Box
An alert box
is often used if you want to make sure information comes through to the user.
When an
alert box pops up, the user will have to click "OK" to proceed.
Syntax
window.alert("sometext");
The
window.alert() method can be written without the window prefix.
Example
alert("I
am an alert box!");
»
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
var
r = confirm("Press a button");
if
(r == true) {
x = "You pressed OK!";
}
else {
x = "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
var
person = prompt("Please enter your name", "Harry Potter");
if
(person != null) {
document.getElementById("demo").innerHTML =
"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
alert("Hello\nHow
are you?");
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