Just got back from the prompt.get function

Question

Just got back from the prompt.get function

Currently, I am utilizing the prompt package in Node to gather user input on the command line. However, my query lies in how I can store and access the return variable from prompt.get? As a newcomer to Node, I'm not entirely sure about the process.

const prompt = require('prompt');

prompt.start();
prompt.get(['num'], function (err: any, result: any) {
    if (err) { return Error(err); }
    if(result.num > 0) {
        return "Positive";
    }
    else {
        return "Negative";
    }
});

Cheers!

javascript npm user-input prompt

Answer 1

Answer №1

To avoid the issue of an empty variable, initialize it outside the callback function and then set its value inside the callback:

let value;

prompt.get(['num'], function (err: any, result: any) {
    if (err) { return Error(err); }

    value = result > 0 ? "Positive" : "Negative";
});

However, keep in mind that the value will still be empty until the callback is complete. Therefore, calling the variable immediately after may result in it being undefined.

let value;

prompt.get(['num'], function (err: any, result: any) {
    if (err) { return Error(err); }

    value = result > 0 ? "Positive" : "Negative";
});

console.log(value); // => undefined

If you prefer using promises, the package also supports that approach where you can utilize await, as demonstrated on their readme page:

(async () => {
    const { num } = await prompt.get(['num']);
})();

Take note of the self-executing async function used here as await only functions within async functions (though technically not required after node v15 & while using modules).

Answer 2

To avoid the issue of an empty variable, initialize it outside the callback function and then set its value inside the callback:

let value;

prompt.get(['num'], function (err: any, result: any) {
    if (err) { return Error(err); }

    value = result > 0 ? "Positive" : "Negative";
});

However, keep in mind that the value will still be empty until the callback is complete. Therefore, calling the variable immediately after may result in it being undefined.

let value;

prompt.get(['num'], function (err: any, result: any) {
    if (err) { return Error(err); }

    value = result > 0 ? "Positive" : "Negative";
});

console.log(value); // => undefined

If you prefer using promises, the package also supports that approach where you can utilize await, as demonstrated on their readme page:

(async () => {
    const { num } = await prompt.get(['num']);
})();

Take note of the self-executing async function used here as await only functions within async functions (though technically not required after node v15 & while using modules).

Just got back from the prompt.get function

Answer №1

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