摘要:
可选链 ?. let name let info = { name: '2323' } info = null // info = undefined // info = '' name = info?.name || '张三'; // 效果和下面 if 一样 if (info && info.na 阅读全文
摘要:
let obj = {} let k = '' for (k in obj) { } if (!k) { console.log('空对象'); } else { console.log('非空对象'); } let num = Object.keys(obj).length if (num) { 阅读全文
摘要:
let y = new Date().getFullYear() let m = new Date().getMonth() + 1 let lastDay = new Date(y, m, 0).getDate() console.log('lastDay: ', lastDay); // las 阅读全文