if (document.frmMain.POL_NO.value == "")
{
alert("Select Policy Number");
document.frmMain.ENDT_NO.value="";
document.frmMain.POL_NO.focus();
return false;
}
Can anyone explain the above code to me? I am new to Javascript.
It appears to be a bit of validation code to make sure a user has entered a value for an item referred to as "Policy Number". It is the sort of code that gets called when submitting a form to check that the values the user has entered are valid.
In detail:
if(document.frmMain.POL_NO.value == "")
Only run this code if the item called in POL_NO the form called frmMain doesn't have a value yet.
alert("Select Policy Number");
Display a message to tell the user that they need to enter a value.
document.frmMain.ENDT_NO.value="";
Set the ENDT_NO item of frmMain to a blank value.
document.frmMain.POL_NO.focus();
Set the focus to the POL_NO item (the same as the user tabbing to it or clicking on it).
return false;
Return false to the code that called the function that this code is in. If this code is used in the event handler for the submit button on a form then returning false will stop the form from being submitted to the server until the POL_NO item has a value.
If the contents of the item POL_NO from the form frmMain is empty, then throw an alert and change the value of the ENDT_NO item value to nothing (empty) and after that focus on the element POL_NO. Return false after that (I assume this code executes at onSubmit event, so the form won't be submitted if POL_NO doesn't have a value)
Probably the logic is that the ENDT_NO can't have a value if POL_NO is empty.
Enjoy!
return false will abort the form submission. Also this code is rather IE specific and will probably not work on many standard browsers. You should use document.getElementById("frmMain").elements["POL_NO"] instead of document.frmMain.POL_NO
<form name="frmMain">. Accessing the input elements like that is fine too.
document.frmMain is a form in the page, and POL_NO and ENDT_NO are fields in the form, presumably listboxes.
This code is a simple validation script to make sure you filled out the form correctly.
//if POL_NO hasn't been set (no policy number selected):
if(document.frmMain.POL_NO.value == "")
{
//show a message box
alert("Select Policy Number");
//clear the value (if any) of ENDT_NO
document.frmMain.ENDT_NO.value="";
//set the form focus to POL_NO (select it, as if you had clicked on it)
document.frmMain.POL_NO.focus();
//stop the form from being submitted
return false;
}
I'm assuming this code is part of a function which is called by frmMain's onSubmit event (and event handler) -- when the function returns false the submit is cancelled. Were this not here, it would show the message box, clear ENDT_NO, select POL_NO and then submit anyways.
Note that referencing members of a form in the document.formName.fieldName.property fashion is deprecated. The correct way is to use getElementById or a similar function:
document.frmMain.ENDT_NO.value = ""; //bad
document.getElementById("ENDT_NO").value = ""; //correct
your HTML document has this defined somewhere in its content
<form id="frmMain" ...>
<input type="..." id="POL_NO">
<input type="..." id="ENDT_NO">
</form>
So. Your script checks whether your POL_NO input field has a value.
ENDT_NO field's value andPOL_NO field - so the user can immediately start selecting/typing a value in this fieldBased on the logic of this script, the business process obviously doesn't allow any value in ENDT_NO field, until there's a value in POL_NO.
If you need to change something about this code (if there's a bug in it), I strongly suggest you get to know Javascript/DOM/HTML before doing any changes.
Actually your code does a pretty simple validation, just read the code and find the fields POL_NO and ENDT_NO in your HTML output. Here is my comments :
// if your POL_NO field is empty,
if(document.frmMain.POL_NO.value == "")
{
// warn user that he need to select Policy number
alert("Select Policy Number");
// set ENDT_NO field's value to empty
document.frmMain.ENDT_NO.value="";
// set POL_NO active - focussed
document.frmMain.POL_NO.focus();
return false;
}
If the value of the input named POL_NO in the form frmMain is empty, then show a message "Select Policy Number", empty the input named ENDT_NO, give the focus to the input named POL_NO, and the exit the function with the return value "false".
