ajax request object

If you are making two independent ajax request, you have to create two independent ajax request object.

function checkA(){
     var request = createRequest();
}

function checkB(){
     var request = createRequest();
}

You might think you have created two independent request object. In fact, you only create one request object. This might make your system prone to error.

the better way

function checkA(){
     var requestForA = createRequest();
}

function checkB(){
     var requestForB = createRequest();
}

By removing "var", we can make the request object become a global variable and make sure each request only coping with one ajax request.