I am trying to make the mandatory fields in my inout form have a red border when the page is loaded and they are empty, and then back-to-normal styling when they have data inside. It isn't working...

I have this code:

Page:

<form method="post" action="xxx.php" enctype="multipart/form-data" value="multipart/form-data" onl oad="borderColour()">

<div>
    <label for="firstName">First Name:</label><br>
    <input type="text" name="firstName" id="firstName" placeholder="First name &hellip;">
</div>

<div>
    <label for="lastName">Last Name:</label><br>
    <input type="text" name="lastName" id="lastName" placeholder="Last name &hellip;">
</div>

</form>

Javascript:

// Border colour for input web forms
function borderColour() {

var firstName = document.getElementById('firstName').value;
var lastName = document.getElementById('lastName').value;
var firstNameId = document.getElementById('firstName');
var lastNameId = document.getElementById('lastName');

  if(firstName == '') {
       firstNameId.addClass("form-required");
     } else {
   firstNameId.removeClass("form-required");
       }
  if(lastName == ''){
       lastNameId.addClass("form-required");
     } else {
       lastNameId.removeClass("form-required");
       }
}

CSS:

form-required {border: 2px solid red !important;}

CodePudding user response：

Here is a working snippet

// Border colour for input web forms
function borderColour(e) {
  if(e.target.value == '') {
     e.target.setAttribute("class", "form-required");
  } else {
     e.target.removeAttribute("class");
  }
}

var inputs = document.querySelectorAll('input');

inputs.forEach(function(el){
  el.onpropertychange = borderColour;
  el.oninput = borderColour;
});

.form-required {border: 2px solid red !important;}

<form method="post" action="xxx.php" enctype="multipart/form-data" value="multipart/form-data" onl oad="borderColour()">

<div>
    <label for="firstName">First Name:</label><br>
    <input type="text" name="firstName" id="firstName" placeholder="First name &hellip;">
</div>

<div>
    <label for="lastName">Last Name:</label><br>
    <input type="text" name="lastName" id="lastName" placeholder="Last name &hellip;">
</div>

</form>

CodePudding user response：

First, you should consider moving the event listening to the script

You can use querySelectorAll() here to get a node list of all the inputs instead of selecting each one individually

const inputs = document.querySelectorAll("input");

inputs.forEach(function (input, index) {
  input.addEventListener("input", () => toggleClass(index));
});

Then you should create a function to toggle the class using classList.add() and classList.remove() instead of addClass()

const toggleClass = (index) => {
  if (inputs[index].value === "") {
    inputs[index].classList.add("form-required");
  } else {
    inputs[index].classList.remove("form-required");
  }
};

CodePudding user response：

I'd suggest using CSS rather than JavaScript:

input,
input:placeholder-shown {
  /* default <input> styles */
  border: 1px solid red;
}
input:not(:placeholder-shown) {
  /* has a value entered */
  border-color: gray;
}

References:

CodePudding user response：

I cant add a comment so, I see that your css selector missing a dot to define a class. If that is not the problem let me know.

EDIT FOR A REAL ANSWER:

Ok the problem is you are using AddClass() as a function but it is a jQuery function. You need to use .classList.add("form-required") method instead. And same with the removeClass method. Instead you should use .classList.remove("form-required")

And dont forget to call your function after the function definition. Like this:

borderColour();

Final Advise

But you need an event listener instead of calling your function once on page load. So you need to add this function to maybe a keypress event on the inputs.

Sample Solution

HTML

<form id="theForm" method="post" action="xxx.php" enctype="multipart/form-data" value="multipart/form-data" onl oad="borderColour()">

<div>
    <label for="firstName">First Name:</label><br>
    <input type="text" name="firstName" id="firstName" placeholder="First name &hellip;">
</div>

<div>
    <label for="lastName">Last Name:</label><br>
    <input type="text" name="lastName" id="lastName" placeholder="Last name &hellip;">
</div>

</form>

CSS

.form-required {border: 2px solid red !important;}

Javascript(Pure Vanilla)

// Border colour for input web forms
function borderColour() {

// You could use below comment to select all inputs but you will probably need to select a textarea too. So selection is a next step. 
//var inputs = document.querySelectorAll('input');
var firstNameSelector = document.getElementById('firstName');
var value = firstNameSelector.value;
  console.log(firstNameSelector.value);
  if(value == '') {
       firstNameSelector.classList.add("form-required");
     }
  else {
   firstNameSelector.classList.remove("form-required");
       }

}
//Adding an event listener to the form element. If you click outside the form you will get the class toggle if the input is empty it will get the red border an so on...
document.getElementById("theForm").addEventListener("focusout", borderColour);

You can add the event listener to all the input elements but to do that you will need a loop(maybe a foreach) like in the other answers.