Old IE JavaScript doesn't support indexOf

Question

From input file type i am passing fullPath(entire local path name) to javascript , and i have written javascript to know the file extension type ,

 while (fullPath.indexOf("\\") != -1)
            fullPath = fullPath.slice(file.indexOf("\\") + 1);
        alert(fullPath);

I have problem in IE only at above part , exactly i found indexOf is not supported in IE, how may i alter my this . If that is not the case is there any alternate to know the file extension which can work in all browsers.

thanks,
michaeld

Answer 1

You could create it (Javascript Code to create method)

For ease of use:

if(!Array.indexOf){
   Array.prototype.indexOf = function(obj){
       for(var i=0; i<this.length; i++){
          if(this[i]==obj){ 
             return i; 
          }
       } 
       return -1; 
     }
 }

Answer 2

indexOf() is supported in IE, at least as far back as version 3.0, assuming you are trying to use it on strings. I believe support for indexOf() on arrays was finally added in IE9.

The example you include in your question is using indexOf() on variables called fullPath and file, which I would assume are strings, but why are you mixing up a while condition on the index within fullpath with a slice operation that uses the index within file:

while (fullPath.indexOf("\\") != -1)
  fullPath = fullPath.slice(file.indexOf("\\") + 1);
// what is the file variable ^^

To work out the file type you want all the characters after the last ".", so try using the lastIndexOf() function:

var fileType = fullPath.slice(fullPath.lastIndexOf(".") + 1);

(Add your own else case for when there is no "." in the string.)

As an aside, I wouldn't assume that the filesystem uses the "\" character to separate folder names: what about non-Windows systems?