.preventDefault() not working in on.('input', function{})

问题

I would like to limit number of chars in my editable div to 10. After user reach the limit I would like to use .preventDefault() method to protect the div from additional chars. Can You help me out, please?

JSFiddle https://jsfiddle.net/7x2dfgx6/1/

HTML

<div class="profileInfo" id="About" style="border:solid;" contenteditable="true">OOOOO</div>

JQuery

    jQuery(document).ready(function($){

    const limit = 10;
    rem = limit - $('#About').text().length;
    $("#counter").append("You have <strong>" + rem + "</strong> chars left.");
    $("#About").on('input', function(event) {
        var char = $('#About').text().length;
        rem = limit - char;
        $("#counter").html("You have <strong>" + rem + "</strong> chars left.");
        if(char>limit)
        {
            event.preventDefault();
            //TODO
        }
    });
});

回答1:

To answer your main question:
.preventDefault() cancel behavior of the events that are cancelable. input event is not .

To check whether an event is cancelable, try: console.log(event.cancelable);.
For input it will say "false"

You may want something like this (untested):

const limit = 10;
var rem = limit - $('#About').text().length;
$("#counter").append("You have <strong>" + rem + "</strong> chars left.");
$("#About").on('input', function(event) {
    var char = $(this).text().length;
    rem = limit - char;
    if(rem <= 0){
        $(this).text($(this).text().slice(0, limit));
    }
    $("#counter").html("You have <strong>" + rem + "</strong> chars left.");
});

EDIT

JSFiddle demo
Since it's contentEditable, I had to use an additional code (from this answer) to set a caret at the end of the input.

回答2:

use keydown instead of input

jQuery(document).ready(function($){

    const limit = 10;
    rem = limit - $('#About').text().length;
    $("#counter").append("You have <strong>" + rem + "</strong> chars left.");
    $("#About").on('keypress', function(event) {
        var char = $('#About').text().length;
        if(char>limit)
        {
            return false;
            //or
            event.preventDefault();
            //TODO
        }
        rem = limit - char;
        $("#counter").html("You have <strong>" + rem + "</strong> chars left.");

    });

});

DEMO

回答3:

Try changing the value of the contenEditable attribute. Also I set the check for the limit to >=

jQuery(document).ready(function($){

    const limit = 10;
    rem = limit - $('#About').text().length;
    $("#counter").append("You have <strong>" + rem + "</strong> chars left.");
    $("#About").on('input', function(event) {
        var char = $('#About').text().length;
        rem = limit - char;
        event.preventDefault();
        if(char>=limit)
        {
            $('#About').attr('contenteditable','False');
            //TODO
        }
        $("#counter").html("You have <strong>" + rem + "</strong> chars left.");
    });

});

回答4:

Here is one way to limit the characters in an input. Works with paste and typing.

/**
 * Limit an inputs number of characters
 * @param {event} e - event of the input the user is typing into
 * @param {number} limit - number of characters to limit to 
 */
function limitInputCharacters(e, limit){
  if(!e){
    return;
  }
  var inputText = e.target.value;
  var charsLeft = limit - inputText.length;
  if (charsLeft >= 0) {
    // do something, or nothing
  } else if (charsLeft < 0) {
    e.target.value = inputText.slice(0, limit)
  }
}

document.addEventListener("DOMContentLoaded", function() {
  const aboutTextArea = document.getElementById('input-about');
  aboutTextArea.addEventListener("input", function(e) {
    limitInputCharacters(e, 300)
  })
})

来源：https://stackoverflow.com/questions/32298064/preventdefault-not-working-in-on-input-function

标签

javascript

jquery

html

dom-events

event-propagation