function appendParam(returnStr, name, realValue) {
    if (returnStr !== '') {
      returnStr += '&'
    }
    if (String(realValue) === '[object Object]') {
      realValue = JSON.stringify(realValue)
    }
    const s = encodeURIComponent(realValue)
    returnStr += encodeURIComponent(name) + '=' + s
    return returnStr
  }
@param {string} returnStr
@param {string} name
@param {any} realValue
@returns {string}