Question

How can I access the value of imgWidth? This is giving me undefined.

somejQueryMethod(function() { 
    var imgWidth;
    $("<img/>").attr(
        "src", 
        $("#SomeImgSelector").attr("src")
    ).load(function() {
        imgWidth = this.width;
    });
    // use imgWidth here
    // imgWidth is undefined here
});

Background info: From this SO question I assumed that as imgWidth was being defined outside of the load() method,
it would always be available outside of load(). Which makes me
wonder why define imageWidth there and not in load()?

Answer 1

You can’t use the value there, because it doesn’t exist yet. The callback function in the load command runs after the content has been loaded, and that happens after the function using the load command ends.

Put the code that needs the value inside the callback function for the load command:

...somejQueryMethod(
    function() { 
        var imgWidth;
        $("<img/>").attr("src", $("#SomeImgSelector").attr("src")).load( function() {
          imgWidth = this.width;
          // use imgWidth here
        } );
    }
);