If I make form

<form>

<input type="checkbox" name="checkbox[]" checked="checked" value="1" />

<input type="checkbox" name="checkbox[]" checked="checked" value="2" />

<input type="checkbox" name="checkbox[]" checked="checked" value="3" />

</form>

then

$('form').submit(function (){

console.log($(this).serializeArray())

})

gives only checkbox[]=3

but should give

checkbox[0]=1

checkbox[1]=2

checkbox[2]=3