個人的にJavaScriptでよく使う記法をまとめました
配列
for で回す
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| let cars = ['BMW', 'Volvo', 'Mini']
for (let car of cars) {
console.log(car)
}
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for で回す（index付き）
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| let cars = ['BMW', 'Volvo', 'Mini']
for (let [index, car] of cars.entries()) {
console.log(car)
}
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forEach で回す
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| let cars = ['BMW', 'Volvo', 'Mini']
cars.forEach(car => { console.log(car) })
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値を取り除く
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| let cars = ['BMW', 'Volvo', 'Mini']
cars = cars.filter(car => { return car !== 'Volvo' })
console.log(cars)
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ある値が含まれるかどうか
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| let cars = ['BMW', 'Volvo', 'Mini']
cars.includes('Volvo')
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逆順にする
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| let cars = ['BMW', 'Volvo', 'Mini']
let cars_sort = cars.reverse();
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連想配列（JSON)
初期化
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| for (var member in myObject) delete myObject[member];
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for で回す
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| let person = { full_name: 'John', last_name: 'Doe', age: 25 }
for (let key in person) {
console.log(key)
console.log(person[key])
}
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キーの配列を作成
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| let person = { full_name: 'John', last_name: 'Doe', age: 25 }
Object.keys(person)
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件数を取得
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| let person = { full_name: 'John', last_name: 'Doe', age: 25 }
Object.keys(person).length
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ディープコピー
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| let person = { full_name: 'John', last_name: 'Doe', age: 25 }
JSON.parse(JSON.stringify(person))
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Keyで並び替える
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| onst unordered = {
'b': 'foo',
'c': 'bar',
'a': 'baz'
};
console.log(JSON.stringify(unordered));
const ordered = {};
Object.keys(unordered).sort().forEach(function(key) {
ordered[key] = unordered[key];
});
console.log(JSON.stringify(ordered));
|
参考
https://stackoverflow.com/questions/5467129/sort-javascript-object-by-key
配列を csv ファイルとしてダウンロードする
https://code-maven.com/create-and-download-csv-with-javascript
参考
https://www.w3schools.com/js/js_loop_for.asp