element 可编辑表格方向键操控

饿了么框架做可编辑表格时想优化体验做个方向键操控，
网上搜到的代码不太满意，自己写了个

/**
 * 键盘移动工具类，使用方法如下
 * <pre>
 * <template slot-scope="scope">
 *    <el-input v-model="scope.row.valuesScore"
 *      v-bind:ref="'r'+ scope.$index + 'c' + 1"
 *      @keydown.native="keyup($event, scope.$index, 1)"></el-input>
 * </template>
 *
 * import {tableKeyMove} from "../util/tableKeyMove"
 *
 * keyup(ev, row, col) {
 *   tableKeyMove(this, ev, row, col, this.tableData.length, 6)
 * },
 * </pre>
 */
export function tableKeyMove(_this, ev, row, col, rowCount, colCount) {
  // 替代 switch 的优雅写法
  const actions = {
    'ArrowUp': () => {
      row--
      if (row < 0) row = rowCount - 1
    },
    'ArrowDown': () => {
      row++
      if (row >= rowCount) row = 0;
    },
    'ArrowLeft': () => {
      if (ev.target.selectionEnd !== 0) {
        return
      }
      col--
      if (col < 1) col = colCount;
    },
    'ArrowRight': () => {
      if (ev.target.selectionEnd !== ev.target.value.length) {
        return
      }
      col++;
      if (col > colCount) col = 1
    },
    'Enter': () => {
      col++
      if (col > colCount) {
        // 右下角的话保持不动
        if (row === (rowCount - 1)) {
          col = colCount
        } else {
          col = 1
          row++
        }
      }
    },
  }
  let action = actions[ev.key];
  if (action !== undefined) {
    action.call()
    // 用 nextTick 避免 input 还没渲染出来
    _this.$nextTick(() => {
      _this.$refs['r' + row + 'c' + col].focus()
    })
  }
}