Simplify jQuery validation

Question

I wrote a script for validate the input field for following requirements

1. Not null
2. Multiple of hundreds
3. Less than needed amount

Here is my script:

    $('#investAmount,#invest-button').bind('keypress', function(event){         
        if(event.which == 13){
            if(amountValidation('#investAmount','#inNeedAmt','#invalidAmt','#mult100','#needAmtValidation')){
                return false;
            }
            else{$(elementId).removeClass('errorField');}
        }
    });
    $('#invest-button').click( function(event){
        if(amountValidation('#investAmount','#inNeedAmt','#invalidAmt','#mult100','#needAmtValidation')){
            return false;
        }
        else{$(elementId).removeClass('errorField');}
    });



function amountValidation(elementId,needAmt,errorMsgId,errorMsgId2,errorMsgId3){    
    var gvAmount =$(elementId).val();

    var errAmount = gvAmount == '';
    if(errAmount == true){$(elementId).addClass('errorField');}
    $(errorMsgId).toggle(errAmount);

    var errGVAmount = !errAmount && !gvAmount.match(/^[1-9]\d*00$/);
    $(errorMsgId2).toggle(errGVAmount); 
    if(errGVAmount == true){$(elementId).addClass('errorField');}

    var errNeedAmount =parseInt($(needAmt).val()) <  parseInt(gvAmount);
    $(errorMsgId3).toggle(errNeedAmount);
    if(errNeedAmount == true){$(elementId).addClass('errorField');}

    return errAmount || errGVAmount || errNeedAmount;   
}

Actually I am going to use this function in my website multiple places please help me to make this better script. My jsfiddle is here

Answer 1

I'm not much of a jQuery freak, but I still have some points on this code. In your amountValidation function, you have some duplication and overhead:

if(errAmount == true)

can be written:

if(errAmount)

Also you always do the same thing when an error occurs, but that's in each statement:

if(errAmount == true){/* mark the field */};  
if(errGVAmount == true){ /* mark the exact same field */};
if(errNeedAmount == true { /* and yet the same thing again */ };

you can shorten this to:

if(errAmount || errGVAmount || errNeedAmount){ /*mark field*/ };

---

Your variable names could use some change too:

errAmount on the first look is like the geeneral error overall, not that amount is null / empty.
You could use errAmountNull instead.

errNeedAmount sounds like you have no amount given yet, which would be errAmount.
I would use errAmountTooSmall instead

Nobody knows, what the GV in errGVAmount stands for.
From the requirements I would call it: errAmountUnallowedValue