为什么indexOf不能在IE8阵列上运行？ [英] Why doesn't indexOf work on an array IE8?

问题描述

以下功能适用于Opera，Firefox和Chrome。但是，在IE8中它在 if（allowed.indexOf（ext [1]）== -1）部分失败。

The below function works fine on Opera, Firefox and Chrome. However, in IE8 it fails on the if ( allowed.indexOf(ext[1]) == -1) part.

有谁知道为什么？有没有明显的错误？

Does anyone know why? Is there any obvious mistake?

function CheckMe() {
    var allowed = new Array('docx','xls','xlsx', 'mp3', 'mp4', '3gp', 'sis', 'sisx', 'mp3', 'wav', 'mid', 'amr', 'jpg', 'gif', 'png', 'jpeg', 'txt', 'pdf', 'doc', 'rtf', 'thm', 'rar', 'zip', 'htm', 'html', 'css', 'swf', 'jar', 'nth', 'aac', 'cab', 'wgz');
    var fileinput=document.getElementById('f');
    var ext = fileinput.value.toLowerCase().split('.');
    if ( allowed.indexOf(ext[1]) == -1) 
    {
        document.getElementById('uploadsec').innerHTML = document.getElementById('uploadsec').innerHTML;
        alert('This file type is not allowed!');
    }
}

推荐答案

版本IE9之前的IE没有 .indexOf（） 函数用于定义确切的规范版本，在尝试使用它之前运行它：

Versions of IE before IE9 don't have an .indexOf() function for Array, to define the exact spec version, run this before trying to use it:

if (!Array.prototype.indexOf)
{
  Array.prototype.indexOf = function(elt /*, from*/)
  {
    var len = this.length >>> 0;

    var from = Number(arguments[1]) || 0;
    from = (from < 0)
         ? Math.ceil(from)
         : Math.floor(from);
    if (from < 0)
      from += len;

    for (; from < len; from++)
    {
      if (from in this &&
          this[from] === elt)
        return from;
    }
    return -1;
  };
}

这是来自MDN ，用于Firefox / SpiderMonkey。在IE等其他情况下，它会添加 .indexOf（） 如果它丢失了......此时基本上是IE8或以下。

This is the version from MDN, used in Firefox/SpiderMonkey. In other cases such as IE, it'll add .indexOf() in the case it's missing... basically IE8 or below at this point.

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