array list - Javascript Python Ruby

配列の作成

let fruits = ["apple", "orange", "banana"];

fruits = ["apple", "orange", "banana"]

配列の値を呼び出す

let fruits = ["apple", "orange", "banana"];

console.log(fruits[0]);

fruits = ["apple", "orange", "banana"]

print(fruits[0])

配列かどうか調べる

let arr = [];

console.log(Array.isArray(arr));

arr = []

print(type(arr) is list)

戻り値は真偽値

配列の最初と最後に要素を追加する

content

let  fruits = ["apple", "orange", "banana"];

// 最初に追加
fruits.unshift("cherry");

// 最後に追加
fruits.push("peach"); 

console.log(fruits);

fruits = ["apple", "orange", "banana"]

# 最初に追加
fruits.insert(0, "cherry")

# 最後に追加
fruits.append("peach")

print(fruits)

配列の最初と最後の要素を削除する

let  fruits = ["apple", "orange", "banana"];

// 最初の要素を削除
fruits.shift();

// 最後の要素を削除
fruits.pop();

console.log(fruits);

fruits = ["apple", "orange", "banana"]

# 最初の要素を削除
fruits.pop(0)

# 最後の要素を削除
fruits.pop()

print(fruits)

配列の要素の数を数える

let  fruits = ["apple", "orange", "banana"];

console.log(fruits.length);

fruits = ["apple", "orange", "banana"]

print(len(fruits))

特定の値の出現回数をカウントする

let  num = [1, 2, 1, 3, 4, 5, 1, 6];
let count = num.filter(n => n === 1).length;

console.log(count);

num = [1, 2, 1, 3, 4, 5, 1, 6]
print(num.count(1))

配列を空にする

let  num = [1, 2, 1, 3, 4, 5, 1, 6];

num.length = 0
console.log(num)

num = [1, 2, 1, 3, 4, 5, 1, 6]
num.clear()
print(num)