# JavaScript

| Type                     | MDN                                                                                                         |
| ------------------------ | ----------------------------------------------------------------------------------------------------------- |
| Array                    | [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array)               |
| Date                     | [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date)                |
| Object                   | [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)              |
| String                   | [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)              |
| JSON                     | [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON)                |
| Set                      | [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set)                 |
| RegExp                   | [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp)              |
| Destructuring Assignment | [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Destructuring_assignment) |
| const                    | [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/const)                   |
| let                      | [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/let)                     |
| export                   | [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/export)                  |

### Variable declarations

`var`

* function scoped
* can be redeclared and updated
* hoisted and initialized with `undefined` as a value

`let`

* block scoped
* declaring in a for loop, inside an if or in a plain block is not going to let the variable "escape" the block
* only use `let` to reassign the variable
* while `let` and `const` are hoisted but not initialized

`const`

* immutable
* block-scoped
* default to `const`

### Array

* <https://sdras.github.io/array-explorer/>
* <https://flaviocopes.com/javascript-array/>

### Object

* <https://sdras.github.io/object-explorer/>
* <https://codepen.io/thonly/pen/JOdwKM>

### Promises

When you go to a restaurant, the hostess gives you a buzzer for your table. When the table is ready, the buzzer buzzes. You respond by sitting at the table.

The buzzer is a promise. It buzzes when the promise resolves, or is ready. The buzz is your handler.

```javascript
var buzzer = new Promise();

fetchTableAsync(hostess => {
    var table = hostess.prepareTable();
    hostess.informServer();
    buzzer.resolve(table);
});

buzzer.then(table => me.sitAtTable(table));
```

* <https://github.com/wbinnssmith/awesome-promises>

### Currying

Currying is a process to reduce functions of more than one argument to functions of one argument with the help of lambda calculus.

```javascript
multiply = (n, m) => (n * m)
multiply(3, 4) === 12 // true

curryedMultiply = (n) => ( (m) => multiply(n, m) )
triple = curryedMultiply(3)
triple(4) === 12 // true
```

* <https://blog.benestudio.co/currying-in-javascript-es6-540d2ad09400>