ie-maxlength-bug-fix.js

/**
 * Internet Explorer's maxlength bug fix
 *
 * @author keik <k4t0.kei@gmail.com>
 * @license MIT
 * 
 * [ref]
 * https://support.microsoft.com/ja-jp/kb/2922126
 *
 * The workaround in the above article could causes other problems such as render issues.
 * This patch fix only the maxlength bug.
 */
function fixMaxLengthForIE() {
  'use strict';

  var DEFAULT_MAX_LENGTH_VALUE = 524288;

  // only IE
  if (window.navigator.userAgent.match(/MSIE|Trident/)) {

    // remove `maxlength' property which causes the bug, and save the value to `data-maxlength' property.
    Array.prototype.concat.apply([], document.querySelectorAll('input[maxlength]')).forEach(function (el) {
      el.setAttribute('data-maxlength', el.maxLength);
      el.maxLength = DEFAULT_MAX_LENGTH_VALUE;
    });

    // on keypress in input[maxlength], if value exceeds maxlength, prevent default action.
    document.body.addEventListener('keypress', function (e) {

      if (Array.prototype.indexOf.call(document.querySelectorAll('input[maxlength]'), e.target) === -1) {
        return true;
      }

      var inputEl = e.target,
          maxlength = parseInt(inputEl.getAttribute('data-maxlength')),
          isValid  = inputEl.value.length - (inputEl.selectionEnd - inputEl.selectionStart) < maxlength;

      if (!isValid) {
        e.preventDefault();
      }
      return isValid;
    });

    // on decide conversion of IME in input[maxlength], cut length of inputed value.
    document.body.addEventListener('keyup', function (e) {

      if (Array.prototype.indexOf.call(document.querySelectorAll('input[maxlength]'), e.target) === -1) {
        return;
      }

      var inputEl = e.target,
          maxlength = parseInt(inputEl.getAttribute('data-maxlength'));

      if (e.keyCode === 13 /* Enter key code when IME available */) {
        inputEl.value = inputEl.value.substr(0, maxlength);
      }
    });

    // on change input[maxlength], cut length of inputed value.
    document.body.addEventListener('change', function (e) {

      if (Array.prototype.indexOf.call(document.querySelectorAll('input[maxlength]'), e.target) === -1) {
        return;
      }

      var inputEl = e.target,
          maxlength = parseInt(inputEl.getAttribute('data-maxlength'));

      inputEl.value = inputEl.value.substr(0, maxlength);
    });
  }
}

// apply
fixMaxLengthForIE();