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indexOf in < IE9

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Aug 18.2012

IE8 reports indexOf is not a supported method. I’m using this to get the value of an array item.

However, MS say IE6+ should be supported; [url]http://msdn.microsoft.com/en-us/library/53xtt423(v=vs.94).aspx[/url]

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JavaScript

6 Comments(s) ↴

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@bionoidAug 18.2012 — All String objects/literals have a indexOf method, if you however passed in a number or boolean etc, then you will have to convert it to String() first:

[CODE]alert( [COLOR="red"]'Test'[/COLOR].indexOf('e') ); //1
alert( [COLOR="Red"]String([/COLOR][COLOR="Blue"]123[/COLOR][COLOR="red"])[/COLOR].indexOf('3') ); //2[/CODE]
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@ldoodleauthorAug 18.2012 — I am passing a string already;

j = b.indexOf(photoUrl);

with photoUrl being a parameter, such as /images/subfolder1/subfolder2/image.jpg

Maybe the / in the string are ****ing it up?
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@bionoidAug 18.2012 — But what is the value of "b", as that is where the problem would b ?
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@Logic_AliAug 18.2012 — IE8 reports indexOf is not a supported method. I'm using this to get the value of an array item.

However, MS say IE6+ should be supported; http://msdn.microsoft.com/en-us/library/53xtt423(v=vs.94).aspx[/quote]

That article refers to String().indexOf not Array().indexOf which is of much more recent introduction.

Here's the crutchware that you need:if( Array().indexOf === undefined )
{
Array.prototype.indexOf = function( item )
{
for( var i = this.length - 1; i &gt; -1 &amp;&amp; this[ i ] !== item; i-- )
;

<i> </i>return i;
}
}
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@ldoodleauthorAug 19.2012 — That article refers to String().indexOf not Array().indexOf which is of much more recent introduction.[/QUOTE]

Thankyou very much. I have seen other variants of your code but they didn't seem to work.

?

EDIT: I noticed yours uses triple = rather than double. Why? Also some of the other articles on the MS website use triple (http://msdn.microsoft.com/en-us/library/jj155295(v=vs.94))
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@Logic_AliAug 22.2012 — I noticed yours uses triple = rather than double. Why? Also some of the other articles on the MS website use triple (http://msdn.microsoft.com/en-us/library/jj155295(v=vs.94))[/quote]

Strict type checking is always good practice.

Actually I now realise that code isn't right, and having looked at the specs, the function allows an optional starting index to be used, so I re-wrote it:
<i>
</i>
Array.prototype.indexOf = Array.prototype.indexOf || function( item, idx )
{
var retVal = 0,
startIndex = ( typeof idx === 'number' ? Math.abs( Math.floor( idx ) ) : 0 );

for( var i = startIndex, len = this.length; i &lt; len &amp;&amp; this[ i ] !== item; i++ )
;

return i == len ? -1 : i;
}

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