text: var XXX = function(x1) {
      let x = x1.toString()
      let sign = ''
      if (x.substr(0,1) === '-') {
          sign = '-'
          x = x.slice(1)
      }
      let strList = []
      for (let i = x.length; i --; i >0) {
          strList.push(x[i])
      }
      let str = sign + strList.join('')
      let m = 1
      for (i = 0; i < 31; i++) {
          m *= 2;
      }
      if (Number(str)>0-m   &&  Number(str) <m ) {
          return str;
      } else {
          return 0
      }
  };
  
  