JavaScript：验证表单字段（图片扩展名）

Question

I'm trying to validate the file extension of a input type="file" field. But even if I upload a correct file it gives me error. I've read W3Schools and other sites and I can't see whats wrong with my code:

http://pastebin.com/GwE0aVaf - It's the IF-statement at the bottom of the first function.

Thanks in advance.

Answer 1

The problem is that in the if statement it will always be true . You got:

if(fileName.lastIndexOf(".jpg") == -1 || fileName.lastIndexOf(".png") == -1)

And one of them will always be true wich causes the whole expressiont o be true. Probably you will want to use AND( && ) instead of OR( || ).

if(fileName.lastIndexOf(".jpg") == -1 && fileName.lastIndexOf(".png") == -1)

The solves the imediate problem, but this type of check will always be faulty, since if the filename is some like "c:\\sample.jpg.zip" it will be valid.

You should validate if the extension is in the end of the string with a endsWith() function or apropriate Regex.

See more at endsWith in JavaScript .