DIALOG BOX IN JAVASCRIPT

INTERACTING WITH USERS:

JavaScript provides these built-in top-level functions for interacting with the user:

·         alert(string): Pop-up a box to alert user for important information. The user will have to click "OK" to proceed. alert() returns nothing (or undefined).

·  prompt(string, defaultValue): Pop-up a box to prompt user for input, with an optional defaultValue. prompt() returns the user's input as a string.

For example,

var number1 = prompt('Enter the first integer:');

var number2 = prompt('Enter the second integer:');

alert('The sum is ' + number1 + number2);                       // Concatenate two strings

alert('The sum is ' + (parseInt(number1) + parseInt(number2))); // Add two numbers

·         confirm(string): Pop-up a box and ask user to confirm some information. The user will have to click on "OK" or "Cancel" to proceed. confirm() which returns a boolean value.

For example,

var isFriday = confirm("Is it Friday?");  // Returns a boolean

if (isFriday) {

   alert("Thank God, it's Friday!");

} else {

   alert('Not a Friday');

}

·         document.write(string) and document.writeln(string): Write the specified string to the current document. writeln() (write-line) writes a newline after the string, while write() does not.