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Detecting language using JavaScript

In Chapter 5, “JavaScript in the Browser,” you were introduced to the

navigator

object and its proper-

ties. One of the properties that has not been discussed in detail is the

language

property, which returns

the language and country code in which the browser is currently operating (for example, “en-us” for

United States English):

var sLang = navigator.language; //won’t work in IE

Mozilla, Opera, and Safari/Konqueror all support this property, but Internet Explorer does not.

Instead, Internet Explorer provides three properties:

browserLanguage

(indicates the language being

used by the browser),

userLanguage

(essentially identical to

browserLanguage

), and

systemLanguage

(indicating the language of the operating system). The

userLanguage

property is essentially the same as

language

, so you can make a simple addition to the previous code to detect the language for all

browsers:

var sLang = navigator.language || navigator.browserLanguage;

Using this code, you can determine if someone is viewing your page from a browser with an unsupported

language setting and take appropriate action, such as redirecting the visitor to a more appropriate page:

if (sLang.toLowerCase() == “fr”) {

document.location.replace(“index_fr.htm”);

}

This code checks to see if the language is French (represented as

“fr”

), and if so, it redirects to another page.

Strategies

The most important step in internationalizing your JavaScript is to avoid hard-coded strings. For example,

don’t do this:

alert(“The date you entered is incorrect.”);

In this example, the string

“The date you entered is incorrect.”

is hard-coded. When a value is

hard-coded, its value cannot be changed without directly editing the line that uses it. Compare this with

the following example:

var sIncorrectDateMessage = “The date you entered is incorrect.”;

//more code here

alert(sIncorrectDateMessage);

You may have noticed that this code uses

toLowerCase()

on the language string.

This is necessary because capitalization is not consistent across browsers. Some

report United States English as

“en-us”

, whereas others use

“en-US”

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Deployment Issues

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