如何检查JavaScript中是否不存在某些字段

Question

I have jquery code like

      for(var j in indivudvalbookdetails) {
         if(indivudvalbookdetails[j]['status'] == "") {
          ... 
         }
     }

Now there might be some items in the loop where status field won't exists, if there are such items the code in the if condition should work.

Please help!!!

Answer 1

Just check if its undefined:

if(typeof indivudvalbookdetails[j]['status'] === "undefined") { ...

Answer 2

Your code is comparing your variable to an empty string. But if this variable is not defined, it can't compare it, so you can do :

if(indivudvalbookdetails[j]['status'] == undefined)

If the « status » var is defined but just empty you can do

 if(indivudvalbookdetails[j]['status'] == null)

Answer 3

你这样检查

if(!indivudvalbookdetails[j]['status'])

Answer 4

Try this:

var myElement =  indivudvalbookdetails[j]['status'];
if (typeof(myElement) != 'undefined' && myElement != null)
{
  // exists.
}

You can also try with JQuery like:

if ($('#elementId').length > 0) {
  // exists.
}