ajax formdata : Illegal invocation

Question

I try to make ajax script for upload for Symfony 2. Chrome returns this error:

Uncaught TypeError: Illegal invocation jquery.min.js:4

Answer 1

jQuery tries to transform your FormData object to a string, add this to your $.ajax call:

processData: false,
contentType: false

Answer 2

it occurs sometime when jquery internally not serialize data correctly data to fix it add this.

cache : false,
dataType    : 'json',
processData : false,