Check selected file matches accept attribute on an <input> tag

Question

I wish to prevent the user from uploading a file the server will reject from a page with minimal JavaScript on it, ideally without adding any heavy dependencies like jQuery

Answer 1

This one gathers the techniques from the other posts and make it to a short and easy function, working with multiple expressions:

verifyAccept = function( file-type, accept ) {
    var type-regex = new RegExp( accept.replace( /\*/g, '.\*' ).replace( /\,/g, '|' ) );
    return type-regex.test( file-type );
}

instead of looping through the splitted accept string it uses regular expression features, just replace , through | which means the single expressions are or'ed.