ES2020 (ES11)
-------------

Another set of useful functionalities used often in MapStore from ES2020.

Optional Chaining
*****************

Shortener for null or undefined (nullish) checks, returning ``undefined`` if something is nullish in the chain.

In the example below, // if ``obj.attr1`` doesn’t have ``attr2``, you have an error


.. code-block:: javascript

    const obj = {
        attr1: {}
    };
    const a = obj.attr1.attr2.attr3;
    // ERROR:
    // Uncaught TypeError: Cannot read property 'attr3' of undefined


To prevent issues you usually needed to do something like this...

.. code-block:: javascript

    const a = obj.attr1 && obj.attr1.attr2 && attr1.attr2.attr3;

This method anyway has a set of issues:

* long
* Implicit conversion can anyway have false positive (e.g. when you have numeric or boolean values).

with optional chaining you can shorten the operation above this way:

.. code-block:: javascript


    const a = obj?.attr1?.attr2?.attr3;

it can be used for:

.. code-block:: javascript

    // object properties
    obj?.prop
    // object props accessed with [] operator
    obj?.["expr"]
     // arrays
    arr?.[1]
    // functions, prevents errors if function is undefined on function call.
    func?.(args)

Nullish Coalescing
******************

Returns default values in case of nullish.
Is more secure than the usual ``&&`` ``||`` checks, because it works also in case of values 0 or empty strings (that are false)

.. code-block:: javascript

    const a = null;
    const foo = a ?? 'default string';
    console.log(foo);
    // expected output: "default string"

    const baz = 0 ?? 42;
    console.log(baz);
    // expected output: 0