用于videojs的javascript中的意外标识符

Question

I get the following error. What's wrong? 137 is the "for (let i = 0, length = array.length; i < length; i++) {" row.

I've uncommented "import videojs from 'video.js';" because I have that code right before this block. Please let me know if that's a problem. It works in some browsers so I'm not sure.

SyntaxError: Unexpected identifier 'i'. Expected either 'in' or 'of' in enumeration syntax. (anonymous function) — plugins.js:137

/*! videojs-playlist-ui - v0.0.0 - 2015-3-12
 * Copyright (c) 2015 Brightcove
 * Licensed under the Apache-2.0 license. */

//import videojs from 'video.js';

// support VJS5 & VJS6 at the same time
const dom = videojs.dom || videojs;
const registerPlugin = videojs.registerPlugin || videojs.plugin;

// Array#indexOf analog for IE8
const indexOf = function(array, target) {
  for (let i = 0, length = array.length; i < length; i++) {
    if (array[i] === target) {
      return i;
    }
  }
  return -1;
};

// see https://github.com/Modernizr/Modernizr/blob/master/feature-detects/css/pointerevents.js
const supportsCssPointerEvents = (() => {
  let element = document.createElement('x');
  element.style.cssText = 'pointer-events:auto';
  return element.style.pointerEvents === 'auto';
})();

const defaults = {
  className: 'vjs-playlist',
  playOnSelect: false,
  supportsCssPointerEvents
};
[...]

Answer 1

Just remove let keyword in all the for loop. I observed JavascriptCore engine in Safari doesn't permit to use temp variables for intialization.