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[JavaScript] Array(配列)のpush()メソッドのサンプルコード50個

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参考:
https://developer.mozilla.org/ja/docs/Web/JavaScript/Reference/Global_Objects/Array/push

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// 1. 単純に数字を追加
let numbers = [1, 2, 3];
numbers.push(4);
console.log(numbers); // [1, 2, 3, 4]

// 2. 文字列を追加
let fruits = ["apple", "banana"];
fruits.push("orange");
console.log(fruits); // ["apple", "banana", "orange"]

// 3. 配列に複数の数字を追加
let scores = [95, 80];
scores.push(100, 90);
console.log(scores); // [95, 80, 100, 90]

// 4. オブジェクトを追加
let users = [{name: "Alice"}, {name: "Bob"}];
users.push({name: "Charlie"});
console.log(users); // [{name: "Alice"}, {name: "Bob"}, {name: "Charlie"}]

// 5. 空の配列に要素を追加
let emptyArray = [];
emptyArray.push(1);
console.log(emptyArray); // [1]

// 6. 複数の文字列を追加
let colors = ["red"];
colors.push("green", "blue");
console.log(colors); // ["red", "green", "blue"]

// 7. 配列に別の配列を追加
let array1 = [1, 2];
let array2 = [3, 4];
array1.push(...array2);
console.log(array1); // [1, 2, 3, 4]

// 8. 条件付きで要素を追加
let conditionArray = [1, 2];
let value = 3;
if (value > 2) {
    conditionArray.push(value);
}
console.log(conditionArray); // [1, 2, 3]

// 9. 計算結果を追加
let calculatedArray = [10, 20];
let result = 10 * 2;
calculatedArray.push(result);
console.log(calculatedArray); // [10, 20, 20]

// 10. 未定義の値を追加
let misc = [null];
let undefinedValue;
misc.push(undefinedValue);
console.log(misc); // [null, undefined]

// 11. 多次元配列に要素を追加
let matrix = [[1, 2], [3, 4]];
matrix.push([5, 6]);
console.log(matrix); // [[1, 2], [3, 4], [5, 6]]

// 12. 配列の長さを増やす
let arrayLength = [1, 2, 3];
arrayLength.push(4);
console.log(arrayLength); // [1, 2, 3, 4]
console.log(arrayLength.length); // 4

// 13. 真偽値を追加
let booleanArray = [true, false];
booleanArray.push(true);
console.log(booleanArray); // [true, false, true]

// 14. 関数を配列に追加
let functionsArray = [];
functionsArray.push(function() { return "Hello"; });
console.log(functionsArray[0]()); // "Hello"

// 15. 配列にプロパティを持つオブジェクトを追加
let objectsArray = [{name: "Alice", age: 25}];
objectsArray.push({name: "Bob", age: 30});
console.log(objectsArray); // [{name: "Alice", age: 25}, {name: "Bob", age: 30}]

// 16. 配列に日付オブジェクトを追加
let dates = [new Date(2023, 0, 1)];
dates.push(new Date(2024, 0, 1));
console.log(dates); // [Date("2023-01-01"), Date("2024-01-01")]

// 17. 配列にnullを追加
let values = [1, 2, 3];
values.push(null);
console.log(values); // [1, 2, 3, null]

// 18. 変数の値を追加
let someValue = 42;
let valueArray = [];
valueArray.push(someValue);
console.log(valueArray); // [42]

// 19. 配列の最後の要素をpushで再追加
let repeatedArray = [1, 2, 3];
repeatedArray.push(repeatedArray[repeatedArray.length - 1]);
console.log(repeatedArray); // [1, 2, 3, 3]

// 20. 文字列と数字を一緒に追加
let mixedArray = [];
mixedArray.push("age", 30);
console.log(mixedArray); // ["age", 30]

// 21. ランダムな数値を追加
let randomArray = [];
randomArray.push(Math.random());
console.log(randomArray); // [0.XXXXXX](ランダムな値)

// 22. 文字列を連結して追加
let greetingArray = [];
let greeting = "Hello, " + "world!";
greetingArray.push(greeting);
console.log(greetingArray); // ["Hello, world!"]

// 23. インデックスを利用して要素を追加
let indexArray = [10, 20, 30];
let index = 1;
indexArray.push(indexArray[index] + 5);
console.log(indexArray); // [10, 20, 30, 25]

// 24. 配列の要素数に基づいて追加
let countArray = ["a", "b"];
countArray.push(countArray.length + 1);
console.log(countArray); // ["a", "b", 3]

// 25. ループを使って複数の要素を追加
let loopArray = [];
for (let i = 0; i < 3; i++) {
    loopArray.push(i * 2);
}
console.log(loopArray); // [0, 2, 4]

// 26. 計算した値を配列に追加
let calculationArray = [];
let x = 5;
let y = 3;
calculationArray.push(x + y);
console.log(calculationArray); // [8]

// 27. 配列に文字列として数値を追加
let stringNumbers = [];
let number = 100;
stringNumbers.push(number.toString());
console.log(stringNumbers); // ["100"]

// 28. プロパティ名を指定してオブジェクトを追加
let namedArray = [];
let object = {};
object["key"] = "value";
namedArray.push(object);
console.log(namedArray); // [{key: "value"}]

// 29. 既存の配列に要素を追加
let existingArray = [1, 2];
let anotherValue = 3;
existingArray.push(anotherValue);
console.log(existingArray); // [1, 2, 3]

// 30. 条件が真のときだけ要素を追加
let conditionalArray = [7, 8];
let condition = true;
if (condition) {
    conditionalArray.push(9);
}
console.log(conditionalArray); // [7, 8, 9]

// 31. 文字列配列に新しい単語を追加
let words = ["hello", "world"];
words.push("JavaScript");
console.log(words); // ["hello", "world", "JavaScript"]

// 32. 小数を配列に追加
let decimals = [];
decimals.push(0.1, 0.2, 0.3);
console.log(decimals); // [0.1, 0.2, 0.3]

// 33. 配列にオブジェクトを動的に作成して追加
let dynamicArray = [];
dynamicArray.push({id: 1, name: "Dynamic Object"});
console.log(dynamicArray); // [{id: 1, name: "Dynamic Object"}]

// 34. 配列に別の配列の要素を追加
let baseArray = [1, 2];
let extraArray = [3, 4];
baseArray.push(...extraArray);
console.log(baseArray); // [1, 2, 3, 4]

// 35. 配列に複数の文字列を連結して追加
let phrases = [];
phrases.push("Hello" + " " + "World");
console.log(phrases); // ["Hello World"]

// 36. 配列にインクリメントされた値を追加
let incrementArray = [0];
incrementArray.push(incrementArray[0] + 1);
console.log(incrementArray); // [0, 1]

// 37. 配列にランダムな文字列を追加
let randomStrings = [];
let possible = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
let randomChar = possible.charAt(Math.floor(Math.random() * possible.length));
randomStrings.push(randomChar);
console.log(randomStrings); // ["ランダムな文字"]

// 38. 配列に条件式の結果を追加
let conditionResultArray = [];
let a = 10, b = 20;
conditionResultArray.push(a > b ? a : b);
console.log(conditionResultArray); // [20]

// 39. 配列に関数の戻り値を追加
function getValue() {
    return 42;
}
let resultArray = [];
resultArray.push(getValue());
console.log(resultArray); // [42]

// 40. 配列に特定の位置の値を複製して追加
let duplicateArray = [5, 10, 15];
duplicateArray.push(duplicateArray[1]);
console.log(duplicateArray); // [5, 10, 15, 10]

// 41. 配列に複数の数値と文字列を混ぜて追加
let mixedValues = [];
mixedValues.push(100, "hello", true);
console.log(mixedValues); // [100, "hello", true]

// 42. 配列にランダムな整数を追加
let randomIntegers = [];
randomIntegers.push(Math.floor(Math.random() * 100));
console.log(randomIntegers); // [ランダムな整数]

// 43. 文字列配列にtoUpperCase()を使って追加
let lowerCaseArray = ["hello"];
lowerCaseArray.push(lowerCaseArray[0].toUpperCase());
console.log(lowerCaseArray); // ["hello", "HELLO"]

// 44. 配列に数値をシフト演算して追加
let shiftedValues = [];
let num = 8;
shiftedValues.push(num << 1);
console.log(shiftedValues); // [16]

// 45. 配列にテンプレートリテラルを使って追加
let templateArray = [];
let name = "Alice";
templateArray.push(`Hello, ${name}`);
console.log(templateArray); // ["Hello, Alice"]

// 46. 配列にオブジェクトのプロパティを動的に追加
let dynamicObjectArray = [];
let key = "dynamicKey";
let dynamicObject = {};
dynamicObject[key] = "value";
dynamicObjectArray.push(dynamicObject);
console.log(dynamicObjectArray); // [{dynamicKey: "value"}]

// 47. 配列にNaNを追加
let nanArray = [];
nanArray.push(NaN);
console.log(nanArray); // [NaN]

// 48. 配列に条件付きで要素を追加(論理積)
let logicalArray = [10];
logicalArray.push(logicalArray[0] && 20);
console.log(logicalArray); // [10, 20]

// 49. 配列にundefinedを条件付きで追加
let optionalArray = [];
let maybeValue;
optionalArray.push(maybeValue || "default");
console.log(optionalArray); // ["default"]

// 50. 配列に多重pushを使用して追加
let multiplePushArray = [];
multiplePushArray.push(1).push(2).push(3);
console.log(multiplePushArray); // [1, 2, 3]
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Comments

onjhthrw368
@onjhthrw368
// 50. 配列に多重pushを使用して追加
let multiplePushArray = [];
multiplePushArray.push(1).push(2).push(3);
console.log(multiplePushArray); // [1, 2, 3]

こんなpush()のメソッドチェーンなんてできませんよ。

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