How to get the filetype of an url string inside a javascript function?

I have two initialization methods: initXML(url) and initJSON(url), which accept an url parameter. The parameter must be an url string that points to an XML or JSON file depending on the function.

What I want to do is to have just one method called init(url) which开发者_Go百科 accepts an url parameter and then calls initXML() or initJSON() based on the filetype of the url parameter string.

e.g. if the url parameter is something like 'content/file.json' call initJSON(), if it is 'other/file.xml' call initXML(), if another filetype return an error.

How can I know this?

Thanks in advance.

Use String.match().

function init(url)
{
    if ( url.match(/\.json$/i) )
    {
        initJSON(); 
    }
    else if ( url.match(/\.xml$/i) )
    {
        initXML();
    }
    else
    {
        throw "Unknown file type";
    }
}

A very quick way of doing it would be to assume that the only period in your URL is at the end, just before the file type:

var type = url.split('.');
type = type[1];

Then the type variable would be either 'json' or 'xml'.

A more foolproof system would be to use regular expressions:

var type = /\.(xml|json)$/.exec(url);
type = type[1];

You could use a regular expression like this:

var isJSON = /\.json$/i;
var isXML = /\.xml$/i;
if( isJSON.test( url ) == true )
  initJSON()
else if( isXML.test( url ) == true )
  initXML()
else
  return( 'error' );