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 HTML5 tag is indicated to be used as container for menu with navigation links in Web site?
<section> <nav> <article>
<nav><ul>
 <li><a href="http://coursesweb.net/css/" title="CSS Course">CSS Course</a></li>
 <li><a href="http://www.marplo.net/jocuri/" title="Flash Games">Flash Games</a></li>
</ul></nav>
Which CSS property shifts an item horizontally to the left or right of where it was?
text-align clear float
.some_class {
  width: 30%;
  float: left;
}
Click on the Math object method which returns x, rounded downwards to the nearest integer.
Math.ceil(x) Math.abs(x) Math.floor(x)
var num = 12.34567;
num = Math.floor(num);
alert(num);       // 12
Indicate the PHP function which returns the number of characters in string.
mb_strlen() count() stristr()
$str = "string with utf-8 chars åèö";
$nrchr = mb_strlen($str);
echo $nrchr;        // 30
The Number and Math Objects

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