".then is not a function" from a very simple inquirer program

the very simple example below (pretty much copied off the npm inquirer front page) is giving the ".then is not a function" error. However I can't figure out what the issue is.

var inquirer = require('inquirer');

inquirer.prompt([
        {
            name: 'my_name',
            type: 'input',
            message: 'What is your name: '
        }]).then(answers => {
                    console.log("Your name is:"+answers.my_name)            
                    });

The error message looks like this:

? What is your name:

/home/peter/Documents/nodejs.d/vscode_examples_workspace/security/inq.js:8
        }]).then(answers => {
            ^

TypeError: inquirer.prompt(...).then is not a function
    at Object.<anonymous> (/home/peter/Documents/nodejs.d/vscode_examples_workspace/security/inq.js:8:13)
    at Module._compile (internal/modules/cjs/loader.js:654:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:665:10)
    at Module.load (internal/modules/cjs/loader.js:566:32)
    at tryModuleLoad (internal/modules/cjs/loader.js:506:12)
    at Function.Module._load (internal/modules/cjs/loader.js:498:3)
    at Function.Module.runMain (internal/modules/cjs/loader.js:695:10)
    at startup (internal/bootstrap/node.js:201:19)
    at bootstrapNodeJSCore (internal/bootstrap/node.js:516:3)

But the following example works OK. So the basic node.js environment (nodejs --version = v9.11.2) is OK.

var inquirer = require('inquirer');

let q = [
    {
        name: 'my_name',
        type: 'input',
        message: 'What is your name: '
    }];

inquirer.prompt (q, function (answers){
    console.log("Your name is: "+answers.my_name);
});

// Output
$ nodejs inq.js
? What is your name:  Peter
Your name is: Peter

This is probably because you have an old version of inquirer (0.12.0 or older) which does not support promises (promises were added in version 1.0.0).

Your snippet works fine with version 6.0.0 and 1.0.0 but fails with the exact same error message in version 0.12.0.

Check packages.json for your version and update it:

"dependencies": {
  "inquirer": "^6.0.0"
}

Then do

npm install