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The Number global object allows us to wrap an object for mathematical use and comes with several useful properties and instance methods. In this lesson we look into Number creation and use some of the properties and methods available with this global object.

We can create our own Number objects using the new special operator or use Number in a non-constructor context to perform type conversion.

Creating a Number object.

Let's look at an example of creating our own Number object and see some Number properties.

// Create our own Number object.
function ourNumber(aValue) {  
  this.aValue = aValue;  
// Inherit from the Number prototype.
ourNumber.prototype = new Number();  
ourNumber.prototype.constructor = ourNumber;
// Min/Max Number Properties.

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Finite and Infinite Numbers.

Let's look at examples of finite and infinite Number properties and test the isFinite global function against these.

 * The isFinite method returns true for all values except 
 * +/- infinity and NaN.
if (isFinite(Number.NEGATIVE_INFINITY)) {
  alert('Number.NEGATIVE_INFINITY is finite');
} else if (isFinite(Number.POSITIVE_INFINITY)) {
  alert('Number.POSITIVE_INFINITY is finite');
} else if (isFinite(NaN)) {
  alert('NaN is finite');
} else {
  alert('Any other value returns true');
// Infinity Properties.
alert(Infinity * Infinity);  

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Some Number Methods.

Let's look at examples of some Number methods.

// The toExponential, toFixed and toLocaleString methods.
aNumber = new Number(1.23456789);

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Number Type Conversion

We can also use Number in a non-constructor context for type conversion.

// Adding a string and number concatenates them.
var aNumber = 12;
var bNumber = '12';
alert(aNumber + bNumber); // 1212 (concatenates)
// Using Number for type conversion.
alert(aNumber + Number(bNumber)); // 24 (adds)

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Lesson 3 Complete

In this lesson we looked at the Number global object and some of its properties and methods.

Related Tutorials

JavaScript 1.5 Basic Tutorials - Lesson 5 - Basic Maths Functions
JavaScript 1.5 Intermediate Tutorials - Lesson 6 - More Maths Functions
JavaScript 1.5 Advanced Tutorials - Lesson 4 - Math

What's Next?

In the next lesson we look at the Math static global object and how to use it.

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