In NodeJS, use Buffer to convert string to hex.

Buffer.from('hello world', 'utf8').toString('hex');

Simple example about how it works:

const bufferText = Buffer.from('hello world', 'utf8'); // or Buffer.from('hello world')
console.log(bufferText); // <Buffer 68 65 6c 6c 6f 20 77 6f 72 6c 64>

const text = bufferText.toString('hex');
// To get hex
console.log(text); // 68656c6c6f20776f726c64

console.log(bufferText.toString()); // or toString('utf8')
// hello world

//one single line
Buffer.from('hello world').toString('hex')

You need to use Buffer.from() for decoding as well. Consider writing a higher-order function to reduce the amount of repeated code:

const convert = (from, to) => str => Buffer.from(str, from).toString(to)
const utf8ToHex = convert('utf8', 'hex')
const hexToUtf8 = convert('hex', 'utf8')

hexToUtf8(utf8ToHex('dailyfile.host')) === 'dailyfile.host'

Sir, If my uint is 10,how to convert 10 to '0x000000000000000000000000000000000000000000000000000000000000000a' by using Node.js?

You can use web3.toHex(number) to convert decimal number to hex then using web3.utils.padLeft("0x0abcdef", 64) to format the hex string to a 64 byte length hex

https://web3js.readthedocs.io/en/1.0/web3-utils.html#padleft

and reverse it from '0x000000000000000000000000000000000000000000000000000000000000000a' to uint 10 ?

just simply use web3.toDecimal() function to convert any hex string to decimal

Here's a node.js specific approach, taking advantage of the the Buffer class provided by the node standard lib.

https://nodejs.org/api/buffer.html#buffer_buffers_and_character_encodings

To get the byte (0-255) value:

Buffer.from('80', 'hex')[0];
// outputs 128

And to convert back:

Buffer.from([128]).toString('hex');
// outputs '80'

To convert to utf8:

Buffer.from('80', 'hex').toString('utf8');

If you have a Buffer, you can call toString() directly and pass the kind of output you want, for example: decryptedPayload.toString('hex')

Converting from a String containing a hex number to decimal and back:

let num = "0xff"; 
console.log(Number(num)); // to decimal 
console.log(`0x${Number(num).toString(16)}`); // to hex notation string