Why doesn t indexOf work on an array IE8

Question

The below function works fine on Opera  Firefox and Chrome  However  in IE8 it fails on the if   allowed indexOf ext 1      -1  part   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

User · Answer

If you re using jQuery  you can use   inArray   instead

User · Answer

If you re using jQuery and want to keep using indexOf without worrying about compatibility issues  you can do this    if   Array prototype indexOf        Array prototype indexOf   function val            return jQuery inArray val  this              This is helpful when you want to keep using indexOf but provide a fallback when it s not available

User · Answer

The problem IE lt  8 simply doesn t have an indexOf   method for arrays   The solution If you need indexOf in IE lt  8  you should consider using the following polyfill  which is recommended at the MDN   if   Array prototype indexOf        Array prototype indexOf   function searchElement  fromIndex            var k          if  this    null                throw new TypeError   quot this quot  is null or not defined                      var o   Object this           var len   o length  gt  gt  gt  0          if  len     0                return -1                    var n    fromIndex    0          if  Math abs n      Infinity                n   0                    if  n  gt   len                return -1                    k   Math max n  gt   0   n   len - Math abs n   0           while  k  lt  len                if  k in o  amp  amp  o k      searchElement                    return k                            k                      return -1            Minified   Array prototype indexOf   Array prototype indexOf function r t  var n if null  this throw new TypeError   quot this quot  is null or not defined   var e Object this  i e length gt  gt  gt 0 if 0   i return-1 var a  t  0 if Math abs a    1 0 amp  amp  a 0  a gt  i return-1 for n Math max a gt  0 a i-Math abs a  0  i gt n   if n in e amp  amp e n    r return n n   return-1

User · Answer

Please careful with   inArray if you want to use it  I just found out that the   inArray is only works with  Array   not with String  That s why this function will not working in IE8   The jQuery API make confusion     The   inArray   method is similar to JavaScript s native  indexOf     method in that it returns -1 when it doesn t find a match  If the   first element within the array matches value    inArray   returns 0   --  They shouldn t say it  Similar   Since indexOf support  String  also

User · Answer

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  gt  gt  gt  0       var from   Number arguments 1      0      from    from  lt  0             Math ceil from             Math floor from       if  from  lt  0        from    len       for    from  lt  len  from                if  from in this  amp  amp            this from      elt          return from            return -1           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

User · Answer

For a really thorough explanation and workaround  not only for indexOf but other array functions missing in IE check out the StackOverflow question Fixing JavaScript Array functions in Internet Explorer  indexOf  forEach  etc

User · Answer

You can use this to replace the function if it doesn t exist    lt script gt  if   Array prototype indexOf        Array prototype indexOf   function elt     from              var len   this length  gt  gt  gt  0           var from   Number arguments 1      0          from    from  lt  0    Math ceil from    Math floor from           if  from  lt  0              from    len           for    from  lt  len  from                  if  from in this  amp  amp  this from      elt                  return from                    return -1            lt  script gt

[javascript] Why doesn't indexOf work on an array IE8?

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