Exiting ES6 features for NodeJS

Setting defaults for function parameters

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function toThePower(value, exponent = 2) {
  // The rest of your code
}
toThePower(1, undefined) // exponent defaults to 2

Extracting Data from Arrays and Objects with Destructuring

TODO

Checking Array Values with Array#includes()

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[1, 2].includes(1) // returns true
[1, 2].includes(4) // returns false

find/findIndex

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let ages = [12, 19, 6, 4];
let firstAdult = ages.find(age => age >= 18); // 19
let firstAdultIndex = ages.findIndex(age => age >= 18); // 1

Allowing Extra Arguments in Functions

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function concat(joiner, ...args) {
  // args is an actual Array
  return args.join(joiner)
}
concat(‘_’, 1, 2, 3) // returns ‘1_2_3’

Expanding Arrays with the Spread Operator

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const arr1 = [1, 2]
const arr2 = [...arr1, 3, 4]
// arr2: [1, 2, 3, 4]
let numbers = [9, 4, 7, 1];
Math.min(...numbers); // 1

for … of

The for...of statement creates a loop iterating over iterable objects (including Array, Map, Set, String, TypedArray, arguments object and so on), invoking a custom iteration hook with statements to be executed for the value of each distinct property.

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// Syntax
for (variable of iterable) {
  statement
}
let iterable = "boo";
for (let value of iterable) {
  console.log(value);
}
// "b"
// "o"
// "o"