如何在控制台中接受用户（JS）的输入？

Question

I tried to create a JavaScript program that outputs the binary format of an English letter on input. I had to put the value in the code. How can the value be entered in the console when the program runs?

function returnBinaryLetter(char) {
  return ((/^[a-z]$/).test(char)) ? char.charCodeAt(0).toString(2).padStart(8, '0') : 'Sorry, that is not a letter.'
}

// Something like:
// const input = consoleInputFunction('Enter a number.');
// console.log(returnBinaryLetter(input.toLowerCase()));

EDIT 1: This is not for a webpage. This is a JS program which I will run using Node.js. I require a solution with just JS, not with some framework (if that is even possible, mentioning just to be specific).

EDIT 2: I have made the code better after suggestions in Endothermic Dragon's answer.

Answer 1

To directly answer your question, you would use prompt to get a user input in this case.

However, you don't need all of that code. Try this:

 function returnBinaryLetter(char) { if ((/^[az]$/).test(char)) { return char.charCodeAt(0).toString(2).padStart(8, '0') } else { return 'Sorry, that is not a letter.' } } var input = prompt('Enter letter to be converted to binary:').toLowerCase(); console.log(returnBinaryLetter(input))

While it may seem a bit intimidating, here's the whole thing broken down:

1. Ask for an input using prompt , and convert it to lowercase.
2. Pass the character to the function returnBinaryLetter , and log the output.

Now for the function returnBinaryLetter :

1. Check if it is a single lowercase letter, using some RegEx.
2. If it is, return binary. Otherwise, return an error with a description.

Hmm, but how does the binary conversion work?

1. First, take the character and get its character code.
2. Next, convert that code to binary.
3. Finally, pad the start so it is an 8-bit number. If it is not 8 digits, add on 0 s at the beginning until it is.

Here, you can see that a more dynamic conversion looks much shorter, and cleaner as well, compared to manually entering about 28 lines of code.

Bonus:

Surprise, surprise. You can further shorten it, Using a ternary operator, you can skip the if-else statement.

 function returnBinaryLetter(char) { return ((/^[az]$/).test(char))? char.charCodeAt(0).toString(2).padStart(8, '0'): 'Sorry, that is not a letter.' } var input = prompt('Enter letter to be converted to binary:').toLowerCase(); console.log(returnBinaryLetter(input))

Now, it's a one-liner!

A ternary operator is usually used within variables when you want to assign its value based on a condition. The ternary operator first checks if the condition inside the brackets is true, and if it is, it returns the first statement (between ? and : ), and if not, it returns the second statement (after the : ). Pairing this with the return statement of a function, you get a one-liner function!

Feedback:

Since it seems that you are following CamelCase , I thought I would mention that function names should always start with a capital letter, along with each word after that also starting with a capital letter. Variables are different however - for variables, you do make the first letter lowercase, but make all the other words uppercase. In addition, the function name returnBinaryLetter might seem intuitive to you, but not for anyone looking at the code. A more intuitive name that exactly describes its function would be LowercaseLetterToBinary .

Answer 2

For NodeJS , You can use inquirer , which provides different kinds of prompts for the command line (such as text, list, checkbox etc).

Prerequistes:

• Install it with npm install inquirer

Example

const { prompt } = require("inquirer");

async main() {
    const binaryLetter = await prompt({
        type: 'input',
        name: 'letter',
        message: `What's your name >>`
    })
    .then(answer => returnBinaryLetter(answer['letter']));
}

main();