How to get file extension in JavaScript?

Posted on

How to get file extension from a file name in JavaScript?

For examples,

For “file.txt”, I want to get “txt”.
For “file2.multi.ext.fileext”, I want to get “fileext”.

This JavaScript function works well for me.

function getExt(filename)
{
    var idx = filename.lastIndexOf('.');
    // handle cases like, .htaccess, filename
    return (idx < 1) ? "" : filename.substr(idx + 1);
}

It handles situations that the filename has no extensions like “.htaccess” and “filename”.


//This is fine if you know that there will be a nothing but a file name in "fileName" 
function getExt(fileName){
     return (fileName.lastIndexOf('.') < 1) ?   null : fileName.split('.').slice(-1);
}

//this is better for unexpected path data like: "/weird.folder/somefolder"
function getExt(path){
    return (path.match(/(?:.+..+[^\/]+$)/ig) != null) ? path.split('.').slice(-1): 'null';
}

Eric Ma

Eric is a systems guy. Eric is interested in building high-performance and scalable distributed systems and related technologies. The views or opinions expressed here are solely Eric's own and do not necessarily represent those of any third parties.

One comment

Leave a Reply

Your email address will not be published. Required fields are marked *

Related Posts