Return false on condition of jQuery post callback

Question

I have a pretty complicated function which does a couple of AJAX posts on submitting a form, to verify values. Depending on the values returned from the POSTs the submit should either work or fail. I thought this could be done using a global boolean and setting its value to either true or false throughout the function, then checking at the end if the boolean had been changed to 'true' and if so call 'return false;'.

This is failing though. I've read up around it and I think it's because the AJAX call is asynchronous so the code isn't executed in sequence.

My code is like this:

  $('.to-step-3').click(function(){
var shape = '';
blnError = false;
$.post('/base/RoomBuilder/GetRoomShape.aspx', function(data) {
  if(data.substring(0,5) == 'Error'){
    alert(data);
    blnError = true;
  }else{
    shape = data;

    $.post('/base/RoomBuilder/GetRoomDimensions.aspx', function(data2) {
      if(data2.substring(0,5) == 'Error'){
        alert(data2);
        blnError = true;
      }else{
        var arrDims = data2.split('_');
        var l =  arrDims[0];
        var w =  arrDims[1];
        var sl = arrDims[2];
        var ll = arrDims[3];
        var sw = arrDims[4];
        var lw = arrDims[5];
        var failMessage = 'Please enter all required dimensions to build your room';

        switch(shape) {
          case 'square':
            if(!(notNullOrEmpty(l))){
              alert(failMessage);
              blnError = true;
            }
          break;
          case'rectangle':
            if(!(notNullOrEmpty(l)) || !(notNullOrEmpty(w))){
              alert(failMessage);
              blnError = true;
            }
          break;
          case'lshaped':
            if(!(notNullOrEmpty(sl)) || !(notNullOrEmpty(ll)) || !(notNullOrEmpty(sw)) || !(notNullOrEmpty(lw))){
              alert(failMessage);
              blnError = true;
            }
          break;
          case'lshapedalt':
            if(!(notNullOrEmpty(sl)) || !(notNullOrEmpty(ll)) || !(notNullOrEmpty(sw)) || !(notNullOrEmpty(lw))){
              alert(failMessage);
              blnError = true;
            }
          break;
        }
      }
    });


  }
});

if(blnError == true){
  return false;
}else{
  return true;
}

});

I found an example of something similar jquery - return value from callback function (in post request) into the function its inside of? but am struggling to get my head around it in the context of what I need to do (I'm admittedly not great at Javascript!)

Could anyone please point me in the right direction here as I've been staring at this way too long! Thanks all.

score 1 · Accepted Answer · answered Jan 03 '12 at 15:38

jQuery post is async by nature so before the ajax response comes the if condition has already been executed. If you want to make execution wait untill ajax response comes then you can use jQuery ajax setting async property to false. Try this

$.ajax({
   url: '/base/RoomBuilder/GetRoomDimensions.aspx',
   async: false,
   type: 'post',
   success: function(){
       //Your logic here
   }
});

//Now check the condition here
if(blnError == true){
  return false;
}else{
  return true;
}

score 0 · Answer 2 · answered Jan 03 '12 at 15:39

0

The simplest way to solve your problem would be to just make it a synchronous call,

$.ajaxSetup({async: false});

$.post(..);

$.ajaxSetup({async: true});

answered Jan 03 '12 at 15:39

Andrew

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Return false on condition of jQuery post callback

2 Answers2