(date.getFullYear () +"") Why does the number add""to make it a string type you can use substr
export function formatDate(date, fmt) {
if (/(y+)/.test(fmt)) {
fmt = fmt.replace(RegExp.$1, (date.getFullYear() + "").substr(4 - RegExp.$1.length));
}
let o = {
"M+": date.getMonth() + 1,
"d+": date.getDate(),
"h+": date.getHours(),
"m+": date.getMinutes(),
"s+": date.getSeconds()
};
for (let k in o) {
if (new RegExp(`(${k})`).test(fmt)) {
let str = o[k] + "";
fmt = fmt.replace(RegExp.$1, (RegExp.$1.length === 1) ? str : padLeftZero(str));
}
}
return fmt;
}
function padLeftZero(str) {
return ("00" + str).substr(str.length);
}