[js: Filter falsy from Array] #js

filter_falsy_from_array.js

// https://qiita.com/akameco/items/1636e0448e81e17e3646

// 普通に評価
const arr = [1, 2, 3, null, 5, undefined, false, 7]
const x = arr.filter(v => v)
console.log(x) // [ 1, 2, 3, 5, 7 ]

// Boolean ぶち込んでも良い
const arr = [1, 2, 3, null, 5, undefined, false, 7]
const z = arr.filter(Boolean)
console.log(z) // [ 1, 2, 3, 5, 7 ]

filter_truthy.ts

// type script だと filter(Boolean) が type safe じゃない
// https://stackoverflow.com/questions/43118692/typescript-filter-out-nulls-from-an-array
//
['', 0, undefined, null, NaN, false].flatMap(v => v ? [v] : []) // []