Javascript variable scope within onload function

This question already has an answer here:

What is the scope of variables in JavaScript? 25 answers

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You're accessing b outside the function it was declared in.

The local scope is function-oriented.

so in:

window.onload = function() {
    var b = "b";
    var p = new Person();
    p.doIknowAorB()'
}

b is a local variable for the anonymous (un-named) function which is connected to onload.

but inside the function doIknowAorB in p :

Person.prototype = function(){
    function doIknowAorB() {
        console.log(a);
        console.log(b);
    };
    return {
        "doIknowAorB": doIknowAorB
    }
}();

There is obviously no b . You can access a as it's a global variable.

---

Because b becomes a local variable or a private variable of the anonymous function.

Scope in javascript is function oriented.

So, it cannot be accessed outside that function block.

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