How to put a static message into an HTML form if the field is empty?-CodePudding

What if I want to check if the field is empty?

If the field is empty I want to send/append a static message like "Hello guys" which is e.target.value.

If I do a check (if the e.target.value == null), nothing happens.

<form id="user_form" action="" method="post" enctype="text/plain">
  <textarea id="msg" cols="30" rows="10" placeholder="Write a message"></textarea>
  <input type="submit" onsubmit="return test()" id="sendBtn" value="send" >
</form>

<!-- Send msg to whatsapp -->
<script>
  const url = 'https://api.whatsapp.com/send?phone=123456789&text=';
  document.getElementById('msg').addEventListener('keyup', (e) => {
    document.getElementById('user_form').setAttribute('action', url   e.target.value);
    console.log(document.getElementById('user_form').getAttribute('action'));
  });
</script>

What I want to do is:

if (e.target.value == "") {
   e.target.value = "This is a default message"
}

CodePudding user response：

Check if the textarea is empty with document.querySelector('#msg').value.length. If the length === 0then it means that the textarea has no text. You can use a ternary conditional operator for that.

You also should implement a trim() inside your condition to check if the text only contains spaces.

document.querySelector('button').addEventListener('click', function() {
  let msg = document.querySelector('#msg');
  let text = (msg.value.trim().length != 0) ? msg.value : 'no text';
  console.log(text);
})

<textarea id="msg" cols="30" rows="10" placeholder="Write a message"></textarea>
<button>Get content of textarea</button>

CodePudding user response：

try e.target.value === ""