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【javascript】配列の置き換え

Last updated at Posted at 2020-12-23

#constで定義したい

配列を定義する時に、後にArray.filter()等の結果に置き換える理由でletを用いてました。
この事に何か違和感を感じていたので、constで定義できるように関数を用意した、ただそれだけです。

exmaple1.js
let array = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
array = array.filter(x => x < 5);

こんな感じに。

exmaple2.js
const array = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
renewArray(array, array.filter(x => x < 5));

#コード

const argumentsError = (argValue, nth, len='-', fnName='') => 
	console.error(`wrong arg(${nth} of ${len}) / ${fnName} function\n`, argValue);

const renewArray = (...args) => {
	//引数検査
	for (let i=0; i<2; i++) {
		if (!Array.isArray(args[i])) return argumentsError(args[i], i+1, 2, 'renewArray');
	}
	//本体
	const [baseArray, newArray] = args;
	baseArray.length = 0;
	baseArray.push(...newArray);
};


const array = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
renewArray(array, array.filter(x => x < 5));

#これ必要?
必要とも言えるし、不要とも言える。

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