In Gecko/Firefox I got the error message:

TypeError: fr.readAsDataurl is not a function

Using the following JavaScript:

var fr = new FileReader();
fr.readAsDataURL(files[i]);

In Gecko/Firefox I got the error message:

TypeError: fr.readAsDataurl is not a function

Using the following JavaScript:

var fr = new FileReader();
fr.readAsDataURL(files[i]);

• javascript
• filereader

• @MartijnPieters I asked the question in the fashion others who will encounter it would ask and posted the answer in the fashion fitting to the situation. Are you suggesting that I post the answer inside of the question? That wouldn't make logical sense. – John Commented May 16, 2015 at 14:23
• 1 Ah, sorry, I missed that you had created a self-answer here. My mistake! – Martijn Pieters Commented May 16, 2015 at 14:42
• 1 Thanks . Ran into the same problem – 32teeths Commented Jul 2, 2015 at 0:29
• 1 @32teeths The best way to thank on Stack is up-voting questions and/or answers. I post in spite of the fact that people are in a rush to down-vote what I post to help people. – John Commented Jul 2, 2015 at 19:34

1 Answer 1

As it turns out someone at Mozilla created the deprecated method readAsDataurl with the improper letter casing and since JavaScript is case sensitive I simply had to use the readAsDataURL method (uppercase URL):

if (fr.readAsDataURL) {fr.readAsDataURL(files[i]);}
else if (fr.readAsDataurl) {fr.readAsDataurl(files[i]);}

Note that the standard/proper casing method is detected first. If you want your code to work as quickly as possible performance will improve over time as standards support improves.