当出现Uncaught (in promise) ReferenceError: username is not defined 错误时

Uncaught (in promise) ReferenceError: username is not defined的出现是： 未给变量或者常量定义导致的

做表单元素正则检查时，代码如下：

//表单元素正则检查
function element(username,pwd){
    const userres = /^[a-zA-Z0-9]{8,30}$/
    const pwdres = /^[a-zA-Z0-9]{6,30}$/
    let userisOK = userres.test(username)
    let pwdisOK = pwdres.test(pwd)
    return userisOK && pwdisOK
}

然后验证的时候出现了报错 最后发现是未给变量或者常量定义导致的，犯了很低级的错误给补充了
let username
let pwd
就解决了

//表单元素正则检查
let username
let pwd
function element(username,pwd){
    const userres = /^[a-zA-Z0-9]{8,30}$/
    const pwdres = /^[a-zA-Z0-9]{6,30}$/
    let userisOK = userres.test(username)
    let pwdisOK = pwdres.test(pwd)
    return userisOK && pwdisOK
}