proof-of-work

pow.js

// 使用前先安装 md5 模块 : npm install md5
const md5 = require("md5")

// 时间戳截取长度 , 从后向前截取
const LENGTH = 6

// check proof of work data
const checkPow = (randomTxt, timestamp) => {
    let [numStr] = getTimeState(timestamp)
    let randMd5Str = md5(randomTxt)
    return randMd5Str.indexOf(numStr) != -1

}

/**
 * 获取 [截取字符串,时间戳] 
 * 
 * @param {long} fixedTimestamp 固定时间戳，可选，如果设置了则 numStr 以该时间戳截取
 * @returns [numStr,timestamp] 
 */
const getTimeState = (fixedTimestamp) => {
    let timestamp = !!fixedTimestamp ? fixedTimestamp : new Date().getTime()
    if(timestamp >>> 38 < 0){
        throw new Error(`${timestamp} is don't look like timestamp type`)
    }
    let timestampStr = timestamp.toString()
    let cutTimestampStr = timestampStr.substr(-LENGTH)
    let num = Number.parseInt(cutTimestampStr)
    let numStr = num.toString(16)
    return [numStr, timestamp]
}

/**
 * generate proof of work data
 */
const pow = () => {
    let [numStr, timestamp] = getTimeState()

    let md5Str = ""
    let count = 0, maxCount = 2000
    let randomStr
    while (md5Str.indexOf(numStr) == -1) {
        randomStr = Math.random().toString(36).substr(3)
        md5Str = md5(randomStr)
        if (count++ > maxCount) {
            [numStr, timestamp] = getTimeState()
            count = 0
        }
    }

    return [randomStr, timestamp]

}

console.time('exhaustive')
let [randomStr, timestamp] = pow()
console.timeEnd('exhaustive')
console.log(`randomStr : ${randomStr} hash(randomStr)=> ${md5(randomStr)} , timestamp : ${timestamp} `)
console.time('check')
console.log(`pow checkout : ${checkPow(randomStr, timestamp)}`)
console.timeEnd('check')