JavaScript function to return an extension for a filename input as a string

gistfile1.js

// @params string - a string containing a file name
// @return string - the file extension (with no period) if it has one, otherwise false

function getFileExtension(string) {
    
    if (typeof(string) === 'string' && (string.indexOf(".") !== -1)){
        var dot=string.indexOf(".");
        return string.substring(dot+1, i.length)
    } else {
        return false;
    }
}