JavaScript 配列とか
#JavaScript
ループと反復処理 · JavaScript Primer #jsprimer
配列かの判定
code:js
const array = [];
console.log(Array.isArray(array)); // => true
console.log(Array.isArray({})); // => false
配列
配列（Array） - とほほのWWW入門
find
callbackの戻り値が真となる最初の要素を返す
Array.prototype.find() - JavaScript | MDN
filter
配列の各要素に対して callback を実行し、callback の戻り値が真であるものの要素からなる配列を返す
Array.prototype.filter() - JavaScript | MDN
code:js
var arr1 = 89, 87, 93, 65, 88;
var arr2 = arr1.filter(function(value, index, array) {
return (value >= 80);
});
console.log(arr2) // => 89, 87, 93, 88
code:js
const fruits = {id: 1, name: 'apple'}, {id: 2, name: 'banana'}, {id: 3, name: 'cherry'}
const deleteId = 2
const redFruits = fruits.filter(v => v.id !== deleteId)
console.log(redFruits) // => {id: 1, name: 'apple'}, {id: 3, name: 'cherry'}
splice(start, n, e1, e2, ...) #splice
0 から数えて、start 番目から n 個の要素を削除し、その代わりに e1, e2, ...を値とする要素を埋め込む
Array.prototype.splice() - JavaScript | MDN
code:js
let arr = "A", "B", "C", "D", "E", "F", "G"
arr.splice(2, 3, "X", "Y", "Z")
console.log(arr) // => "A", "B", "X", "Y", "Z", "F", "G"
配列の要素を順番に処理
code:js
const arr = "Red", "Green", "Blue"
for (let i in arr) {
console.log(arri) // => "Red", "Green", "Blue"
}
some
条件を満たす要素があるかどうか
Array.prototype.some() - JavaScript | MDN
文字列
split
文字列（配列ではない!）を区切り文字で分割して配列にする
String.prototype.split() - JavaScript | MDN
code:js
const str = 'The quick brown fox jumps over the lazy dog.'
const words = str.split(' ')
console.log(words)
// => "The", "quick", "brown", "fox", "jumps", "over", "the", "lazy", "dog."