Converting an int64 value to a Number object in JavaScript
- by Matt
I have a COM object which has a method that returns an unsigned int64 (VT_UI8) value. We have an HTML page which contains some JavaScript which can load the COM object and make the call to that method, to retrieve the value as such:
var foo = MyCOMObject.GetInt64Value();
This value can easily be displayed to the user in a message dialog using:
alert(foo);
or displayed on the page by:
document.getElementById('displayToUser').innerHTML = foo;
However, we cannot use this value as a Number (e.g. if we try to multiply it by 2) without the page throwing "Number expected" errors. If we check "typeof(foo)" it returns "unknown".
I've found a workaround for this by doing the following:
document.getElementById('displayToUser').innerHTML = foo;
var bar = parseInt(document.getElementById('displayToUser').innerHTML);
alert(bar*2);
What I need to know is how to make that process more efficient. Specifically, is there a way to cast foo to a String explicitly, rather than having to set some document element's innerHTML to foo and then retrieve it from that. I wouldn't mind calling something like:
alert(parseInt((string)foo) * 2);
Even better would be if there is a way to directly convert the int64 to a Number, without going through the String conversion, but I hold out less hope for that.
