The interesting "(" and "[" in Javascript

I remember a bet with my colleagues a few years ago, <input id = "txtname" type = "text" size = "2" value = "test" name = "txtname"> the object uses document. all ["txtname"]. value and document. all ("txtname "). which of the two values is correct? In fact, both operations can obtain the value, so no one will lose.

 

But today we have encountered the same problem. I don't know whether the problem is caused by the IE version. The two returned values are different. The former is normal, and the latter cannot get the value.

 

The former obtains a text box object, while the latter obtains the object but does not know what the object is.

 

The specific difference is not clear yet. Find the reason and try again ......