1. The Number object

The Number object is another predefined JavaScript object that offers some useful properties and methods for use with numbers.

Properties of the Number object

- Example:
In the following JS script we create a new property (mult8) to the Number object, this new property multiplies by 8 the value of a variable.
<script type="text/javascript"><!--
var nr = 7;

// creates a new property ( mult8 ) to the Number object
Number.prototype.mul8 = nr*8;

// uses the property "mult8"
document.write(nr.mul8);       // 65
--></script>

Methods of the Number Object


2. The Math object

The Math object is a predefined JavaScript object used for mathematical purposes, it provides constants and functions for more complex operations.
If for example we want to get a random number between 0 and 1, we write:

Properties of the Math object

All of the properties of the Math object contain read-only values, that can be useful in mathematical calculations (They must be written with capital letters). - Example:
<script type="text/javascript"><!--
// find the area of a circle,
var rad = 7.8;           // radius value
var area = Math.PI * (rad * rad);     // gets the area
document.write(area);        // 191.134497044403
--></script>

Methods of the Math Object

The methods of the Math object enable you to perform certain calculations in your scripts.
- Some examples:
1) Alerts the value of the positive square root of 64, which is 8.
<script type="text/javascript"><!--
alert(Math.sqrt(64));         // 8
--></script>

2) Returns the number with the highest value, between 8, 4, 88, 56
<script type="text/javascript"><!--
alert(Math.max(8, 4, 88, 56));       // 88
--></script>

3) The following code would return the value of 4 to the 3rd power
<script type="text/javascript"><!--
alert(Math.pow(4, 3));       // 64
--></script>

- Math.random() only returns numbers between zero and one. If you want to generate a random integer between two integers, you can combine the methods "round()" and "random()", as shown in the following example.
<script type="text/javascript"><!--
// gets an random integer between 1 and 10
var lower = 1;
var higher = 10;
var nr = Math.round(Math.random() * (higher - lower)) + lower;

document.write(nr);
--></script>

Daily Test with Code Example

HTML
CSS
JavaScript
PHP-MySQL
Which attribute specifies the HTTP method (GET, POST) used to submit the form-data?
action method value
<form action="script.php" method="post"> ... </form>
Which CSS property allows to add shadow to boxes?
background-image box-shadow border-radius
#id {
  background-color: #bbfeda;
  box-shadow: 11px 11px 5px #7878da;
}
Which function removes the first element from an array?
pop() push() shift()
var fruits = ["apple", "apricot", "banana"];
fruits.shift();
alert(fruits.length);           // 2
Indicate the function that can be used to check if a PHP extension is instaled.
function() filetype() extension_loaded()
if(extension_loaded("PDO") === true) echo "PDO is available."
The Number and Math Objects

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