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URI methods

This code outputs two values:

http://www.wrox.com/illegal%20value.htm#start

http%3A%2F%2Fwww.wrox.com%2Fillegal%20value.htm%23start

As you can see, the first URI was left intact except for the space, which was replaced with

%20

. The second

URI replaced all non-alphanumeric characters with their encoded equivalents, which essentially makes

this URI useless. This is why

encodeURI()

can be used on full URIs, whereas

encodeURIComponent()

can only be used on strings that are appended to the end of an existing URI.

Naturally, there are also two methods to decode URIs that have already been encoded, called

decodeURI()

and

decodeURIComponent()

. As you might expect, these methods do the exact opposite

of their counterparts. The

decodeURI()

method only decodes characters that have been replaced by

using

encodeURI()

. For instance

%20

is replaced with a space, but

%23

is not replaced because it repre-

sents a pound sign (#), which

encodeURI()

does not replace. Likewise,

decodeURIComponent()

decodes all characters encoded by

encodeURIComponent()

, essentially meaning it decodes all special

values. Example:

var sUri = “http%3A%2F%2Fwww.wrox.com%2Fillegal%20value.htm%23start”;

alert(decodeURI(sUri));

alert(decodeURIComponent(sUri));

This code outputs two values:

http%3A%2F%2Fwww.wrox.com%2Fillegal value.htm%23start

http://www.wrox.com/illegal value.htm#start

In this example, the

uri

variable contains a string that is encoded using

encodeURIComponent()

. The

resulting values show what happens when you apply the two decoding methods. The first value is

the output of

decodeURI()

, which replaced only

%20

with a space; the second value is the output of

decodeURIComponent()

, which replaces all the special characters.

The final method is perhaps the most powerful in the entire ECMAScript language, the

eval()

method.

This method works like an entire ECMAScript interpreter and accepts one argument, a string of

ECMAScript (or JavaScript) to execute. For example:

eval(“alert(‘hi’)”);

This line is functionally equivalent to the following:

alert(“hi”);

These URI methods,

encodeURI()

encodeURIComponent()

decodeURI()

, and

decodeURIComponent()

, replace the BOM methods

escape()

and

unescape()

The URI methods are always preferable because they encode all Unicode characters,

whereas the BOM methods encode only ASCII characters correctly. Avoid using

escape()

and

unescape()

Chapter 3

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