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Prevent user from typing in input at max value

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遥遥无期
遥遥无期 2020-12-30 04:41

I\'d like the user to be blocked from typing more if the value is over 100. So far I have the following from reading different posts:

$(\'.equipCatValidation
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7条回答
  • 無奈伤痛
    2020-12-30 05:21

    Checking keyup is too late, the event of adding the character has already happened. You need to use keydown. But you also want to make sure the value isn't > 100 so you do need to also use keyup to allow js to check the value then too.

    You also have to allow people to delete the value, otherwise, once it's > 100 nothing can be changed.

    <input class="equipCatValidation" type="number" />

    When using input type="number", change also needs to be on the event list.

    $('.equipCatValidation').on('keydown keyup change', function(e){
    if ($(this).val() > 100 
        && e.keyCode !== 46 // keycode for delete
        && e.keyCode !== 8 // keycode for backspace
       ) {
       e.preventDefault();
       $(this).val(100);
    }
});

    http://jsfiddle.net/c8Lsvzdk/

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  • 予麋鹿
    2020-12-30 05:22

    Here's a solution for those using modern vanilla Javascript:

    Just snap the value back down to the max when the user focuses away from the input.

    You would set the input to a number type and the max value

    <input type="number" max="100">

    and then add a function to the onblur method of the element

    document.querySelector('input[max]').onblur = function (event) {
    // If the value is less than the max then stop
    if (Number(event.target.value) < event.target.max) return
    // Snap the value to the max
    event.target.value = event.target.max
}

    You can also use oninput instead of onblur but that may cause the user to have to fight the input in certain situations.

    Example

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  • 感情败类
    2020-12-30 05:24

    Basically keypress events are fired before accepting the current value. So when you press on any key, keypress event is subscribed but you don't get the updated value/result for the recently pressed key. So, to get the last pressed key we can use the fromCharCode method and concat it with the value we got from the textbox. That's it,

    HTML :

    <input id="inputBox" type="text" />

    jQuery :

    $("#inputBox").on("keypress", function(e){
    var currentValue = String.fromCharCode(e.which);
    var finalValue = $(this).val() + currentValue;
    if(finalValue > 100){
        e.preventDefault();
    }
});

    jsFiddle

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  • 予麋鹿
    2020-12-30 05:26

    Maybe keydown instead of keyup?

    <!DOCTYPE html>
<html>
<head>
  <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>

  <script>
  $(function() {

    $('.equipCatValidation').keydown(function(e){
      if ($(this).val() > 100) {            
         e.preventDefault();              
      }
    });

  })
  </script>

</head>
<body>

<input type="text" class="equipCatValidation">

</body>
</html>

    EDIT: There is a valid comment here - Prevent user from typing in input at max value - to circumvent that you should probably store the previous value and restore it when necessary.

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  • 北海茫月
    2020-12-30 05:27 
    <input class="equipCatValidation" />
var maxValue = 100;

    jquery

    $('.equipCatValidation').on('keypress', function(e){
  /* preventing set value when it doesn't pass conditions*/
 e.preventDefault(); 
 var input = $(this);
 var value = Number(input.val());
 var key = Number(e.key);
 if (Number.isInteger(key)) {
     value = Number("" + value + key);
     if (value > maxValue) {
       return false;
     }
     /* if value < maxValue => set new input value 
     in this way we don't allow input multi 0 */
     $element.val(value);
 }
});

    vanilla js

    document.querySelector(".equipCatValidation")
 .addEventListener("keypress", function(e) {
  e.preventDefault();
  var input = e.target;
  var value = Number(input.value);
  var key = Number(e.key);
  if (Number.isInteger(key)) {
    value = Number("" + value + key);
    if (value > maxValue) {
      return false;
    }
    input.value = value;
  }
 });

    example

    addition to the this answer

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  • 旧时难觅i
    2020-12-30 05:38

    It is bad UI to disable the input if a user inputs a bad value. I'm assuming you simply want to put a max value that the user cannot go over. If so, you can either clamp the value, or use the max attribute in your markup:

      <form>
    <input type='number' max='100'>
  </form>

    If you input an invalid value, the input will turn red, and you cannot submit the form.

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