Ask User

A simple CLI prompt to get user input.

Install

$ npm install ask-user

Basic Usage

Promise style

askUser('Are you sure?').then((answer) => {
    /*...*/
});

Async/Await

(async () => {
    const answer = await askUser('Are you sure?');
    /*...*/
})();

askUser (question, limit, isRequired, validate, options)

All arguments are optional.
When called with no question it defaults to: 'Press "ENTER" to continue... '

The askUser function accepts up to 5 argument and their order doesn't matter. It is possible because argument types are all unique. Anything goes:

askUser(question, opts)
askUser(opts, limit, question, isRequired)
askUser(validate, question, limit)
// etc.

• question - string
• limit - number
• isRequired - boolean
• validate - function
• options - object (in parens are the default values)
  • validate - function (Always true)
  • limit - number (None)
  • isRequired - boolean (false)
  • hidden - boolean (false)
  • convert - boolean (true)
  • trailingSpace - boolean (true)
  • timeout - number (None)
  • default - any ('' - Empty String)
  • throwOnTimeout - boolean (false)
  • stdin - Readable Stream (process.stdin)
  • stdout - Writable Stream (process.stdout)

question

The string that precedes the user input. For readability, the question is separated from the answer with a space. You can disable this behavior by setting the trailingSpace option to false.

limit

You can set a maximum number of tries (answer validation fails). The final answer will be set to an empty string (or a default value, if provided) when limit exceeded.

const question = 'You have 3 tries to guess my favorite color:';
const onGuess = (guessColor) => (guessColor === 'blue')
const limit = 3
const answer = await askUser(question, onGuess, limit)

if (answer === '') {
    // failed 3 times
}

isRequired

If you require an answer for your question you can pass in a boolean true. The question will be re-asked if no answer provided.

const answer = await askUser('Username:', true);

validate

A function that is used as the answer handler. It gets called when the user answers the question and hits "Enter".

This is NOT the final callback.

The handler's main purpose is for validating the user input. An invalid input will re-prompt the user with the same question until validation (or Ctrl+C).

You can also use it to manipulate (trim, escape, sanitize etc.) an answer before returning it.

Arguments

• answer <String> - the user's answer
• count <Number> - the number of times the user was prompted with the question. Starts with 1.

const question = 'Are we there yet?';

const finalAnswer = await askUser(question, (answer, count) => {
    // ...
})

Return Value

• Return false if you don't accept the answer. The user will be prompted again with the same question.
• Return true if you accept the user answer. Current answer will be returned as the final answer.
• Return any truthy value (other than a boolean true) to be used as the final answer.
• Return null or undefined to cancel question. Prompt will exit immediately and final answer will be an empty string or a default value (see options below). Could be used as a kind of a cancel/exit.

// The question will be repetitively re-asked until the user types "I DO!"
const finalAnswer = askUser('Will you marry me?', (answer) => {
    return answer === 'I DO!';
});

console.log(finalAnswer) // I DO!

The handler could also function as your answer parser/sanitizer/manipulator:

const question = 'What is your name?';
// user types: "  John " with spaces

const validate = (answer) => {
    const trimmed = answer.trim();

    return trimmed; // final answer: "John"
    // vs.
    return true;    // final answer: "  John "
}

const finalAnswer = await askUser(question, validate)

Default Answer

Another use of returning a value could be a default value:

const question = 'Which branch to pull from?';
const validate = (branch) => {
    if (!branch) return 'master'; // when the answer is empty

    return branch.trim(); // return clean branch name
}

const finalAnswer = await askUser(question, validate)

But you don't need a handler for a simple default. You can simply use a logical OR operator:

const question = 'Which branch to pull from?';
const finalAnswer = await askUser(question) || 'master';

Async Validation

Async handler is also supported. Just make sure to return a promise.

const asyncHandler = (answer) => {
    return new Promise((resolve) => {
        setTimeout(() => {
            if (condition) resolve(true)
            else resolve(false)
        }, 1000)
    });
}

const answer = await askUser(question, asyncHandler)

Exceptions and Promise-Rejections

Throwing exceptions (or rejecting the promise) from within the answer-handler will bubble up for you to catch:

try {
    const answer = await askUser(question, () => {
        const err = new Error("I'm too old for this")

        throw err
        // or:
        return new Promise((resolve, reject) => {
            reject(err)
        })
    });
}
catch (err) {
    // caught here
}

Options

An object with the following possible properties (in parens are the default values):

• validate - function (Always true)
• limit - number (None)
• isRequired - boolean (false)
• hidden - boolean (false)
• convert - boolean (true)
• trailingSpace - boolean (true)
• timeout - number (None)
• default - any ('' - Empty String)
• throwOnTimeout - boolean (false)
• stdin - Readable Stream (process.stdin)
• stdout - Writable Stream (process.stdout)

validate, limit and isRequired are both arguments and options.

NOTE: If you pass in an argument and its alias option, the argument will take precedence.

const answer = await askUser(question, {
    limit: 3,
    isRequired: true,
    validate: (guessColor) => (guessColor === 'blue')
});

hidden - default: false

Set to true to mask user input with stars. Default is false.

const answer = await askUser('Enter Password:', {hidden: true});
// User types: `1234`
// User sees:  `****`

// answer === 1234

convert - default: true

All inputs are strings by default. askUser automatically converts answers into numbers and booleans when possible.

• '42' (string) - becomes 42 (number).
• 'y' / 'Yes' - becomes true.
• 'n' / 'No' - becomes false.

Case insensitive

You can disable this behavior by setting the convert option to false:

// 'Yes' for both questions:

const answer1 = await askUser(question);
// answer1 === true

const answer2 = await askUser(question, {convert: false});
// answer2 === 'Yes'

trailingSpace - default: true

By default, a single space is added after the question if the last character is not a space or a newline. You can disable this behavior by setting the trailingSpace option to false.

await askUser(question, {trailingSpace: false});

default - default: '' (empty string)

A question will resolve with the default value in case of:

• no user input
• validator returns null
• a timeout
• when the tries limit exceeded

When no default value provided the returned value is an empty string. You can set a default value using the default option.

const  = 'Which branch to pull from?';
const answer = await askUser(question , {default: 'master'});

// user doesn't type anything and hits "Enter"

console.log(answer); // 'master'

If you prefer, you can simply use a logical OR operator:

const finalAnswer = await askUser(question) || 'master';

timeout - default: false

You can set a time limit for an answer. Pass the number of seconds to the timeout option:

const question = 'You have 3 seconds to answer or else...';
const answer = await askUser(question , {timeout: 3});

// no answer
console.log(answer); // empty string

throwOnTimeout - default: false

Normally, a timeout will be resolved with an empty string or a default value. Set throwOnTimeout option to true if you want the promise to reject on timeout.

stdin & stdout - default: process.stdio

By default askUser sends the question to the process.stdout and waits for the answer from process.stdin. You can pass other streams using the options object.

const opts = {
    stdin: myInputStream, 
    stdout: myOutputStream
}

const answer = await askUser(question, opts)