在全局名称空间中使用var

Question

I'm reading "you don't know javascript" and I find some trouble with one example in the book "This & Object Prototypes".

When discussing the different rules for this , specifically in the "Implicit binding" paragraph, the author gives this example:

function foo() {
    console.log( this.a );
}

var obj = {
    a: 2,
    foo: foo
};

var bar = obj.foo; // function reference/alias!

var a = "oops, global"; // `a` also property on global object

bar(); // "oops, global"

However when trying this on JSFiddle I get an undefined output in console instead of the "oops, global".

Conversely, if I define a without var or using window.a I get the output intended by the author regardless of strict mode.

Why is this happening? Did something in ES6 change the way global variables should be declared?

Answer 1

The default settings for JS Fiddle wrap the JS in a function and assign it as an load event handler.

Your tests are not in the global scope.