为什么会收到此错误类型错误：无法读取未定义的属性“客户端”

Question

if (arguments.length === 0 || !config.client && !config.dialect) {
                                    ^

TypeError: Cannot read property 'client' of undefined

Why am I getting this error?

Answer 1

The config variable is undefined . You should check it to before reading the values of config.client and config.dialect

if (arguments.length === 0 || (config && !config.client && !config.dialect))

Keep in minds that if config is undefined , the evaluation of the right expression in the OR clause will be false

Answer 2

I was running into this issue as well. In my code I'm initializing knex in the following way.

const knex = require('knex')(process.env.DATABASE_URL)

When I checked the value of process.env.DATABASE_URL I discovered that it was undefined. Once I fixed that, the error went away! (In my case I had my .env file in the wrong place)