如果一个字符串由很多个完全相同的字符串组成，如果只想取其中一个则可以:

test.js:

let targetStr = process.argv.slice(2)[0]              // 获取想要重复的字符串  123456let repeatCount = process.argv.slice(2)[1]            // 获取想要重复的次数    8let resultStr = ''for(let i = 0; i < repeatCount; i++) {  resultStr += targetStr}console.log(resultStr)function countInstances(mainStr, subStr){    let count = 0    let offset = 0    do{      offset = mainStr.indexOf(subStr, offset);      if(offset != -1)      {          count++;          offset += subStr.length;      }    } while (offset != -1)    return count}function findTargetStr(targetStr) {  let len = targetStr.length  for(let i = 0; i < len; i++) {    let str = ''    for (let k = 0; k <= i; k++) {      str += targetStr[k]    }    let count = countInstances(targetStr, str)    if (count * str.length === len) {      console.log(str)      break    }  }}findTargetStr(resultStr)                         // 123456

在shell命令窗口输入: node test.js 123456 8