var ReactLanguage = require('react-language');

/* set currentLanguage, if currentLanguage not set, 
 * use window.navigator.language || window.navigator.userLanguage
 * setLanguage also store the language to localStorage, reopen the web page
 * will getItem from localStorage before get from window.navigator 
 * notice: ReactLanguage converted navigator.language to lower case
 */
ReactLanguage.setLanguage('xxx');


/* create method return a ReactComponent, it must and only pass one argument.
 * if argument === true, this component will be the default component,
 * if no other created component match currentLanguge, this content(children) will show.
 * Ther is only one default component in a project.
 */
const En = ReactLanguage.create(true);


// string argument, if argument === currentLanguage, the content(children) will show.
const Ja = ReactLanguage.create('ja');


// function argument, if return true, the content(children) will show. 
const Cn = ReactLanguage.create(function (currentLanguage) { 
    // notice: currentLanguage was converted to lower case
    return currentLanguage.indexOf('zh-') === 0;
});


....

<div>
    <Cn>你好，世界</Cn>
    <En tag="div">Hello world.</En>
    <Ja>こんにちは世界</Ja>
</div>

======================================================
rendered result:
currentLanguage === 'en-US' => <div><div>Hello world.</div></div>
currentLanguage === 'zh-CN' => <div><span>你好，世界</span></div>
currentLanguage === 'ja' => <div><span>こんにちは世界</span></div>
currentLanguage === 'other language' => <div><div>Hello world.</div></div>