How do I replace placeholder text in a NodeJS script with the value of a variable?

Question

I have a NodeJS script utilizing Nodemailer to send an email with the Linux system information of the device the script is running on once a button is pressed in my application.

Below is a shortened excerpt from the script:

const nodemailer = require('nodemailer');
...
...
 // Message object
    let message = {
        // Comma separated list of recipients
        to: 'Nodemailer <example@nodemailer.com>',

        // Subject of the message
        subject: 'Test message ' + Date.now(),

        // HTML body
        html: `<p><b>Hello</b>, below is some sample system information</p>
        <p>{{ip-address}} {{os-version}}<br/></p>`,

How can I replace the example text {{ip-address}} and {{os-version}} with values from a variable?

Note: One thought I had was perhaps to save the value of a shell command executed by cp.exec to a variable, but my obstacle remains how to pass the contents of that variable to the placeholder text.

The information saved to {{ip-address}} and {{os-version}} isn't static so I can't just set permanent .ENV variables and call it day, I need to get fresh information every time this script is run.

I don't see `{{ip-address}}` or `{{os-version}}` getting any value assigned to them. Where are they being declared and assigned a value? — abhinav, Jan 08 '20 at 18:28
@abhinav Hello, the question itself is asking how to do just that. {{ip-address}} and {{os-version}} are verbatim text in the body of the email that need to be replaced. Any thoughts? — Blumie, Jan 08 '20 at 18:30
Man, I think you need to rephrase the question to `How to get the IP address and OS version of the system in Nodejs` or something similar. From the looks of it, it seems like you are asking a way to replace the variable with its value in a string. — abhinav, Jan 08 '20 at 18:34
@abhinav IP address and OS version are just examples for the purpose of the question, but yes my question is essentially how to replace a value in a long string with the value of a variable. Once I figure that out with the help of the community I can use it as a template to apply to a variety of placeholder values. — Blumie, Jan 08 '20 at 18:37

score 3 · Accepted Answer · answered Jan 08 '20 at 18:38

Since you're using ` notation you can do

html: `<p><b>Hello</b>, below is some sample system information</p>
    <p>${ip-address} ${os-version}<br/></p>`

Javascript inside of the ${} notation will be evaluated and inserted in the string.

Template strings documentation: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Template_literals

How do I replace placeholder text in a NodeJS script with the value of a variable?

1 Answers1