//不带索引
let divCon = document.getElementsByClassName("el-form-item__error");
if (divCon.length > 0) {
    for (var item of divCon) {
      console.log("打印：", item.innerText);
    }
}

//带有索引
let divCon = document.getElementsByClassName("el-form-item__error");
if (divCon.length > 0) {
  for (var i = 0; i < divCon.length; i++) {
     console.log("11", divCon[i].innerText); i是索引值
  }
}