Question

I am modifying a php login form, adding javascript check form function to it. I wish when users tick the checkbox, the form is true, and when the checkbox is empty, the form becomes false. the codes are like these:-

//the javascript
function check_sli(form,mark,edit){
     if(mark==1 || mark=="all"){
     if(form.terms.value==""){
       sli_check_terms.innerHTML="Please read the terms and conditions first！";
       sli_check_terms.style.height="auto";
       return false;
     }else{
       sli_check_terms.innerHTML="";
       sli_check_terms.style.display = "none";     
     }
   }
}

//the form
<form name="form_sli" id = "form_sli" ACTION="<?php echo $loginFormAction1; ?>" METHOD="POST" onSubmit="return check_sli(form_sli,'all')">

<input type="text" name="login"/><br>
<input type="password" name="password"/><br>

<input name="terms" type="checkbox" id="terms" checked="checked" onBlur="check_sli(form_sli,1)">I have read the terms and conditions<br><div id="sli_check_terms" class="right"></div>

<input type="submit" name="button" id="button" value="Login" />
</form> 

The above codes works normal for textfields, such as when the textfield is empty, the innerHTML pops up. However, when using checkbox, I don’t know the checked and unchecked value, is it 1 vs 0, or !==”” vs ==””??? and shall I use onBlur or onSubmit???

How shall it modify the scripts so that it works for checkbox as well? thanksalot!

Answer 1

checkboxes use .checked in the dom, which is a bool.

if (form.terms.checked) {
    ... it's checked ...
}