Scope chain

What is scope chain ? Scoping answer the question "Where you can access a certain variable ?" In javascript each new function create a new scope instead of some others programming languages like PHP, >JAVA etc.. where even an if, for elements create a new scope. A scope is determined where the function is written. Let's see some examples to really understand how scope works.

First example

let a = "hello";
first();

function first() {
    let b = "hi !";
    second();

    function second() {
        let c = "hey !";
        console.log( a + b + c);
    }
}

1. Like the global execution context there is a global scope which is the scope by default in our example the global scope has access to the a variable and also to the first function.
2. We got the first local scope which is the code inside the first function, it means that we can access to the code inside the first function and to his parent scope which is the global scope.
3. Inside the first scope we call an other function second which is defined in the scope of the first function. We now execute the code inside the second function.
4. We execute the console.log function who returns the a, b and c variable, but we don't have access to the a and b variable so the computer will find in the parent scope if it can find the two variables.
5. The scope chain works in descending order, you can access variable of a parent scope and not the opposite.

Current errors

This is a list of the main errors that you can meet when you use scope chain:

Note: I'm not a wizard there is maybe some issue that you notice above so fell free to open an issue in the github repo if you find a new error not mentioned above.