function firstIndex(arr, text) {

      // 若元素不存在在数组中返回-1

      let firstVal = -1;

      for (let i = 0; i < arr.length; i++) {

        // json (arr[i].id == text)

        if (arr[i] === text) {

          firstVal = i;

          return firstVal;

          break;

        }

      }

      return firstVal;

    }

    // json数组

    // let array = [{ id: "1" }, { id: "2" }, { id: "3" }];

    // let text = "2";

    // 普通数组

    let array = [1, 2, 3, 4, 5];

    let text = 3;

    console.log("获取某个元素第一次出现在数组的索引", firstIndex(array, text));