【javascript】全角数字を半角数字に変換

数字に限定すれば変換用のマップを組まなくても良い。

コード

お好きなので

const fullnums = '０１２３４５６７８９';
const reFullnums = new RegExp('['+fullnums+']','g');

const toHalfnums = text => text.replace(reFullnums, m=>fullnums.indexOf(m));

console.log(toHalfnums('あ３６９あ'));     // 'あ369あ'
console.log(toHalfnums('７'));     // '7'

const fullnums = '０１２３４５６７８９';
const toHalfnums = text => text.replace(/[０-９]/g, m=>fullnums.indexOf(m));

const toHalfnums = text => text.replace(/[０-９]/g, m=>'０１２３４５６７８９'.indexOf(m));