Question

function valid() {     begin_checked = false;     end_checked = false;      alert('begin_checked: ' +begin_checked);     alert('end_checked: ' +end_checked);      if (document.dd.begin.checked.length == undefined || document.dd.end.checked.length == undefined )     {         alert('In undefined');     }      alert('end'); } 

When the if statement is false, it never gets to alert(‘end’) ? When it is true, it executes properly. Why?

Answer 1

There is probably a null pointer exception and you do not have errors outputting to your browser.

You need some output to check:

alert(document); alert(document.dd); alert(document.dd.begin); alert(document.dd.begin.checked); alert(document.dd.end); alert(document.dd.end.checked); 

If you get undefined from any of those, then your code will not execute properly.

Edit: Also, the other answers here all have good information. Read those as well.

Edit2: Alternative – Surround your code in a try/catch block and alert the error:

function valid(){      try{         begin_checked = false;         end_checked = false;          alert('begin_checked: ' +begin_checked);         alert('end_checked: ' +end_checked);          if (document.dd.begin.checked.length == undefined || document.dd.end.checked.length == undefined ){             alert('In undefined');         }          alert('end');      } catch (e) {         alert(e);     }  }