我需要使index_to_write變量在函數外部可見。我怎樣才能使這成為可能？const XlsxPopulate = require('xlsx-populate');let found = false;let i = 1;let index_to_write = 0;XlsxPopulate.fromFileAsync("todo-list.xlsx")    .then(workBook => {        while (i <= 10 && found === false){            const value = workBook.sheet("Do-Shopping").cell("A" + i.toString()).value();            if (value === undefined) {                found = true;                index_to_write = i.toString();            }            i++;        }    });console.log("A " + index_to_write + " is the first one to be free of data");我嘗試return index_to_write;在下面添加index_to_write = i.toString();但它不能解決問題。目前，它顯示0，與初始化時一樣，但它應該打印4。如何修復它？非常感謝您！