JavaScript Browser Detection

The Navigator object contains information about the visitor's browser.

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Browser Detection

Almost everything in this tutorial works on all JavaScript-enabled browsers. However, there are some things that just don't work on certain browsers - especially on older browsers.

Sometimes it can be useful to detect the visitor's browser, and then serve the appropriate information.

The Navigator object contains information about the visitor's browser name, version, and more.

 Note: There is no public standard that applies to the navigator object, but all major browsers support it.

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The Navigator Object

The Navigator object contains all information about the visitor's browser:

Example

<div id="example"></div>

<script>

txt = "<p>Browser CodeName: " + navigator.appCodeName + "</p>";
txt+= "<p>Browser Name: " + navigator.appName + "</p>";
txt+= "<p>Browser Version: " + navigator.appVersion + "</p>";
txt+= "<p>Cookies Enabled: " + navigator.cookieEnabled + "</p>";
txt+= "<p>Platform: " + navigator.platform + "</p>";
txt+= "<p>User-agent header: " + navigator.userAgent + "</p>";

document.getElementById("example").innerHTML=txt;

</script>

Try it yourself »

JavaScript RegExp Object

RegExp, is short for regular expression.

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Complete RegExp Object Reference

For a complete reference of all the properties and methods that can be used with the RegExp object, go to our complete RegExp object reference.

The reference contains a brief description and examples of use for each property and method!

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What is RegExp?

A regular expression is an object that describes a pattern of characters.

When you search in a text, you can use a pattern to describe what you are searching for.

A simple pattern can be one single character.

A more complicated pattern can consist of more characters, and can be used for parsing, format checking, substitution and more.

Regular expressions are used to perform powerful pattern-matching and "search-and-replace" functions on text.

Syntax

var patt=new RegExp(pattern,modifiers);

or more simply:

var patt=/pattern/modifiers;

• pattern specifies the pattern of an expression
• modifiers specify if a search should be global, case-sensitive, etc.

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RegExp Modifiers

Modifiers are used to perform case-insensitive and global searches.

The i modifier is used to perform case-insensitive matching.

The g modifier is used to perform a global match (find all matches rather than stopping after the first match).

Example 1

Do a case-insensitive search for "w3schools" in a string:

var str="Visit W3Schools";
var patt1=/w3schools/i;

The marked text below shows where the expression gets a match:

Visit W3Schools

Try it yourself »

Example 2

Do a global search for "is":

var str="Is this all there is?";
var patt1=/is/g;

The marked text below shows where the expression gets a match:

Is this all there is?

Try it yourself »

Example 3

Do a global, case-insensitive search for "is":

var str="Is this all there is?";
var patt1=/is/gi;

The marked text below shows where the expression gets a match:

Is this all there is?

Try it yourself »

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test()

The test() method searches a string for a specified value, and returns true or false, depending on the result.

The following example searches a string for the character "e":

Example

var patt1=new RegExp("e");
document.write(patt1.test("The best things in life are free"));

Since there is an "e" in the string, the output of the code above will be:

true

Try it yourself »

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exec()

The exec() method searches a string for a specified value, and returns the text of the found value. If no match is found, it returns null.

The following example searches a string for the character "e":

Example 1

var patt1=new RegExp("e");
document.write(patt1.exec("The best things in life are free"));

Since there is an "e" in the string, the output of the code above will be:

e

Try it yourself »

JavaScript Math Object

The Math object allows you to perform mathematical tasks.

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Try it Yourself - Examples

round()
How to use round().

random()
How to use random() to return a random number between 0 and 1.

max()
How to use max() to return the number with the highest value of two specified numbers.

min()
How to use min() to return the number with the lowest value of two specified numbers.

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Complete Math Object Reference

For a complete reference of all the properties and methods that can be used with the Math object, go to our complete Math object reference.

The reference contains a brief description and examples of use for each property and method!

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Math Object

The Math object allows you to perform mathematical tasks.

The Math object includes several mathematical constants and methods.

Syntax for using properties/methods of Math:

var x=Math.PI;
var y=Math.sqrt(16);

Note: Math is not a constructor. All properties and methods of Math can be called by using Math as an object without creating it.

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Mathematical Constants

JavaScript provides eight mathematical constants that can be accessed from the Math object. These are: E, PI, square root of 2, square root of 1/2, natural log of 2, natural log of 10, base-2 log of E, and base-10 log of E.

You may reference these constants from your JavaScript like this:

Math.E
Math.PI
Math.SQRT2
Math.SQRT1_2
Math.LN2
Math.LN10
Math.LOG2E
Math.LOG10E

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Mathematical Methods

In addition to the mathematical constants that can be accessed from the Math object there are also several methods available.

The following example uses the round() method of the Math object to round a number to the nearest integer:

document.write(Math.round(4.7));

The code above will result in the following output:

5

The following example uses the random() method of the Math object to return a random number between 0 and 1:

document.write(Math.random());

The code above can result in the following output:

0.6193570049945265

The following example uses the floor() and random() methods of the Math object to return a random number between 0 and 10:

document.write(Math.floor(Math.random()*11));

The code above can result in the following output:

6

JavaScript Boolean Object

The Boolean object is used to convert a non-Boolean value to a Boolean value (true or false).

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Try it Yourself - Examples

Check Boolean value
Check if a Boolean object is true or false.

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Complete Boolean Object Reference

For a complete reference of all the properties and methods that can be used with the Boolean object, go to our complete Boolean object reference.

The reference contains a brief description and examples of use for each property and method!

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Create a Boolean Object

The Boolean object represents two values: "true" or "false".

The following code creates a Boolean object called myBoolean:

var myBoolean=new Boolean();

If the Boolean object has no initial value, or if the passed value is one of the following:

• 0
• -0
• null
• ""
• false
• undefined
• NaN

the object is set to false. For any other value it is set to true (even with the string "false")!