Use Node.js to read content from the terminal

This is the 17th day of my participation in Gwen Challenge

preface

At ordinary times when writing exercise algorithm questions, encounter online written test, most online exercise sites need to write their own input and output, such as the common niuke, Sai Code network. Some people who are not familiar with node.js input and output will feel powerless

Usually such sites provide a readline or read_line method for data entry

Node actually provides a module called readline: reads line by line to do this

The author has used only Leetcode, which only needs to realize functions when writing with JS, and does not need to consider how to input content from the keyboard

This article will share with you the use of Node-readline module through the terminal input content

Simple to use

const readline = require('readline')

const rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout
})

// No newline output
process.stdout.write('Enter two numbers:')
// Listen for enter events
rl.on('line'.(str) = > {
    // STR is the input
    
    const [a, b] = str.split(' ')
    console.log('and is:', (+a) + (+b));
    
    // Closing the line-by-line read stream triggers the closing event
    rl.close()
})

// Listen for close events
rl.on('close'.() = > {
    console.log('Triggered a close event');
})
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The code logic is as follows:

• Enter two numbers
• Calculate the sum of the two figures

Assuming the file above is called index.js, let’s just type and run below

node index.js
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The running results are as follows:

It’s not as comfortable to use as other languages, like:

• C++:cin>>param
• C:scanf("%s",&param)
• C#:param = Console.ReadLine()
• . , etc.

How do you make it as easy for Node.js to input data from a terminal as the language above?

We wrap it with our fingers

encapsulation

const rdl = require('readline')

/** * reads a line */
function readline() {
    const rl = rdl.createInterface({
        input: process.stdin,
        output: process.stdout
    })
    return new Promise(resolve= > {
        rl.on('line'.(str) = > {
            resolve(str)
            rl.close()
        })
    })
}

module.exports = readline
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We are writing a new test.js, and the one above is called read.js in the same directory

const readline = require('./readline')

async function main(){
    process.stdout.write('First word:')
    const a = await readline()
    process.stdout.write('Second word:')
    const b = await readline()
    console.log(a , b);
}

main()
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node test.js
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The results

Now it’s a lot easier to use, it’s a little bit of another language

Other tool method encapsulation

util.js

print

A printing method that does not wrap

function print(str){
    process.stdout.write(str)
}
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Use:

print('hello world\n')
print('666\n')
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readNumber

Read a number. Since readLine reads everything as a string, it needs to convert itself to read a number

const readline = require('./readline')

async function readNumber(){
    return+ (await readline())
}
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Testing:

async function main(){
    const a = await readline()
    const b = await readNumber()

    console.log('a'.typeof a);
    console.log('b'.typeof b);
}

main()
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The results

Methods summarize

We can create an index.js file and export the readline, readNumber, and print methods

const rdl = require('readline')

function print(str){
    process.stdout.write(str)
}

/** * reads a line */
function readline() {
    const rl = rdl.createInterface({
        input: process.stdin,
        output: process.stdout
    })
    return new Promise(resolve= > {
        rl.on('line'.(str) = > {
            resolve(str)
            rl.close()
        })
    })
}


async function readNumber(){
    return+ (await readline())
}


module.exports = {
    print,
    readline,
    readNumber
}
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Practice: Guess the numbers

TODO: Waiting for completion

Data summary

• Readline module: reads line by line
• Article complete sample source code