我可以根据文本的值更改类吗？

Question

I'm okay with JS but I'm not the greatest. So Would it be possible to change the class of an input if the input is less than 3? Simple question, would it be possible for someone to leave a block of code that I can mess with?

Thanks

Answer 1

you have to use ascii method charAt(0) :

 const inText = document.getElementById('in-text') inText.oninput=()=> { if (inText.value.length=1) { inText.className = (inText.value.charAt(0) < '3'.charAt(0)) ? 'green' : 'blue' } }

 #in-text { color: white; font-size:2em; font-weight: bold; } .blue { background-color: darkblue;} .green { background-color:darkgreen;}

 <input type='text' id='in-text' size="1" value="$" class="green">

Answer 2

Yes, you can do something like this.

Let's say you have the input field with type as "number" and some id.

<input type="number" id="numberInput" onkeyup="myFunction()" />

Then the js will be like this

function myFunction() {
   const input = document.getElementById("numberInput");
   if(input.value <= 3){
      input.classList.add("myClass");
   }
}

This will fire an event on each keyup event on the input field. It will add a new class if value is less than three.
You can also fire the event on change(onchange="myFunction()") but the event will be fired only when user clicks away from the input field.