It’s time for another post, this time ES2019 features. Here are all the features and examples:

Array#{flat,flatMap}

[1, 2, 3].flatMap((x) => [x, x * 2]);
// => [1, 2, 2, 4, 3, 6]

[1, [2, [3]]].flat(Infinity);
// => [1, 2, 3]

## Object.fromEntries
javascript
const iterableOfEntries = new Map([
  ['cat', 'dog'],
  ['life', 42]
]);

const obj = Object.fromEntries(iterableOfEntries);
console.log(obj); // { cat: "dog", life: 42 }

## String#{trimStart,trimEnd}
javascript
"  Hey JS!".trimStart(); // "Hey JS!"
"Hey JS!  ".trimEnd();   // "Hey JS!"

## Symbol#description
javascript
const symbol = Symbol('TC39');
console.log(symbol.description); // 'TC39'
console.log(symbol.hasOwnProperty('description')); // false

## Optional Catch Binding
javascript
try {
  throw new Error("End of life!");
} catch { // ✋ no params for catch
  console.log("^ you are dead anyway!");
}

## JSON ⊂ ECMAScript
javascript
// Without the proposal:
"foo<U+2028>bar<U+2029>baz" // → SyntaxError

// With the proposal:
"foo<U+2028>bar<U+2029>baz" // does not throw

## Well-formed JSON.stringify
javascript
JSON.stringify('\uD800');
// → '"\\ud800"'

## Function#toString
javascript
function /* this is bar */ bar () {}
bar.toString();
// 'function /* this is bar */ bar () {}'
// ^ previously this was not the case

## Array#sort Stability
javascript
[
  { name: "Jan", age: 20 },
  { name: "Jhon", age: 20 },
  { name: "David", age: 18 },
  { name: "Ram", age: 18 },
  { name: "Sita", age: 18 },
  { name: "Ravan", age: 18 },
  { name: "Asura", age: 12 },
  { name: "Milly", age: 12 },
].sort((m, n) => m.age - n.age);
// People with the same age retain their order.