====== Javascript ======

===== References =====
  * [[https://www.typescriptlang.org/docs/handbook/utility-types.html|Utility types]]

Popular code styles
  * [[https://github.com/airbnb/javascript|Airbnb]]
  * [[https://github.com/standard/standard |Standard]]
  * [[https://github.com/google/eslint-config-google|Google]]


===== Functional aspects =====
=== find ===
Function ''find()'' returns the first value of an array satisfying a given condition.
<code javascript>
let array1 = [1,4,6,8,12];
let found = array1.find(el => {
   return el > 10
  }
);
//found = 12
</code>

=== map ===
Function ''map()'' applies a specified function to each element in the array.

<code javascript>
var array1 = [1, 4, 9, 16];
const map1 = array1.map(x => Math.pow(x,2));
//map1=[1,16,81,256]
</code>

For more complicated functions
<code javascript>
array1.map(x => {
  //stuff with x
  return x;
})
</code>

=== reduce ===
Function ''reduce()'' executes a given reducer function on every element of the array returning a single value. It consists of accumulator getting information from each element of the array consequently.

<code javascript>
let array1 = [1, 2, 3, 4];
let r = array1.reduce((acc, elem) => acc + elem)
//r = 10
</code>

Initial value ''initVal'' could be specified by
<code javascript>
array1.reduce((acc,elem) => acc + elem, initVal);
</code>

=== every ===
Function ''every()'' checks if a given condition applies to every element of the array.
<code javascript>
const array1 = [true, false, true];
if(array1.every(Boolean)) {
//all conditions met
}
</code>

=== filter ===
Returns a subset of the array satisfying certain conditions
<code javascript>
const data = ["hotel","california", "baby"];
let newdata = data.filter(e => e.length > 5);
</code>

===== Object orientated aspects =====
=== Constructor ===

Constructor shortcut without manually assigning properties to the new instance. 
<code javascript>
export class CartItem {
    id: number;
    name: string;
    description: string;
    unitPrice: number;
    coverPhoto: string;
    quantity: number;

    constructor(data: any) {
        Object.assign(data)
    }
}
</code>

New instance of the class with specified properties can now be created by 
<code javascript>
CartItem({'id': 1, 'name': 'Paper towel', ...})
</code>

===== Syntax =====
Template literals
<code javascript>
const x = 10
console.log("x = ${x}")
const y = `x = ${x}`
</code>

Multiline string
<code javascript>
const s = "SELECT * \
          FROM table \
          WHERE ...";
const t = `one \
           two`
</code>

===== Frameworks =====
  * [[angular|Angular]]
  * [[react|React]]