Javascript检查输入字段是否有价值

Question

Im trying to figure out how can Javascript check if input field has any value, then it removes class value "is-invalid".

I have this code so far:

<form>
<label for="inputName">Username</label>
<input type="text" class="is-invalid" id="inputName">
</form>

<script>
        var checkInput = document.getElementById("inputName");
        if (checkInput.value) {
        element.classList.remove("is-invalid");
        }
</script>

As you can see theres a red border (class="is-invalid") around the input. As soon as user puts any value in the inputfield, Javascript will remove class value "is-invalid".

Or might there be an easier option with jQuery?

Answer 1

You have a mistake in your code. You have used

element.classList.remove("is-invalid");

which is wrong, you have to use it like

checkInput.classList.remove("is-invalid");

You can use like this in javascript.

 function check(){ var checkInput = document.getElementById("inputName"); if (checkInput.value) { checkInput.classList.remove("is-invalid"); } else { checkInput.classList.add("is-invalid"); } } 

 <form> <label for="inputName">Username</label> <input type="text" class="is-invalid" id="inputName" onkeyup="check()"> </form> 

In Jquery you can try like

 $('#inputName').keyup(function(e){ if ($('#inputName').val()) { $('#inputName').removeClass("is-invalid"); } else { $('#inputName').addClass("is-invalid"); } }) 

 <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script> <form> <label for="inputName">Username</label> <input type="text" class="is-invalid" id="inputName"> </form> 

Answer 2

You need to add an event listener to the element to know when it changes.

  var checkInput = document.getElementById("inputName");
    checkInput.addEventListener('keyup', (e)=>{
      if (e.target.value!==''){
        e.target.classList.remove("is-invalid");
    }
  })