JavaScript readAsDataurl is not a function

问题

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]);

回答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.

来源：https://stackoverflow.com/questions/30272619/javascript-readasdataurl-is-not-a-function