在Node JS中将mysql与过程变量连接

Question

I am new to Node JS and was trying to get it connected with MySQL. While studying I came around a snippet which I don't understand. It is as follows:

const mysqlServer = `mysql://${process.env.DB_USERNAME}:${process.env.DB_PASSWORD}@${process.env.DB_SERVER}`;

Can anyone tell what is happening in this? And when I am printing mysqlServer it is giving me the output as :

mysql://undefined:undefined@undefined

Please help..!!

Answer 1

The process object is a global that provides information about, and control over, the current Node.js process. As a global, it is always available to Node.js applications without using require().

— source

The process.env property returns an object containing the user environment. See environ(7) .

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So the code is reading a couple of environment variables and inserting them into the string.

Since you are getting undefined, they are clearly not environment variables that have been defined.

How you define environment variables depends, unsurprisingly, on the environment you are using.

For example, in bash you could:

export DB_USERNAME=example 
export DB_PASSWORD=example
export DB_SERVER=localhost
node myscript.js

(It is possible to do this as a one-liner but then your password can end up in the list of running processes, which is not good for security).