摘要：
let a = undefined; let b = null; let c = ''; let d = 0; let e = {}; let f = []; if (a) { console.log("undefined 能过"); } else { console.log("undefined 不能过"); ... 阅读全文
摘要：
转载：https://blog.csdn.net/github_36496793/article/details/53065870 阅读全文