How to get Cross Browser Compatibilty for window.fileReader API of HTML5

There are multiple pieces that you'll need to check the support of:

//Full File API support.
if ( window.FileReader && window.File && window.FileList && window.Blob )
{
    //Supported
}

else alert( "Not supported" );

Your second requirement:

I also want to know the way to read the file contents without using HTML5 fileAPI... but not using ActiveXObject.

What you could do is this:

1. Have an iframe (you'll be posting to this)
2. Have an input of type "file"
3. When the user selects the local file, you use javascript to post it to the iframe (e.g. document.getElementById( "myForm" ).target = "myIframe"; document.getElementById( "myForm" ).submit();
4. The iframe's POSTed page (Could be PHP) reads the uploaded file contents and does a callback to the parent page (e.g. <script>window.parent.someCallbackFunction( theFileCOntents );</script>)

You can check features with simple if logic and wrap your functionality there.

if ('FileReader' in window) {
  // Do something with FileReader since it's supported
} else {
  // Do something with your polyfill solution
}

You can try a polyfill solutions like this one (works in IE8): https://github.com/Jahdrien/FileReader

You can always use a try-catch to check the FileReader() is supported in a browser.

try {
    var reader = new FileReader();
    //do something
}
catch(e) {
    alert("Error: seems File API is not supported on your browser");
    //do something
}