js 校验括号——括号不可嵌套且需成对出现

<template>
  <div style="padding: 30px">
    <p>校验规则 ：</p>
    <ol>
      <li>括号不能嵌套</li>
      <li>括号必须成对出现</li>
    </ol>
    <el-input
      clearable
      placeholder="请输入例句！"
      v-model="exampleString"
      style="width: 400px"
    ></el-input>

    <p>
      校验结果：
      <span
        :style="{
          color: errorMsg ? 'red' : 'green',
        }"
      >
        {{ errorMsg || "校验通过" }}</span
      >
    </p>
  </div>
</template>

<script>
export default {
  data() {
    return {
      exampleString: "",
      errorMsg: "",
    };
  },
  watch: {
    exampleString(val) {
      this.errorMsg = this.check(val);
    },
  },
  methods: {
    check(str) {
      let errorMsg = "";
      let leftBracketsList = ["(", "（", "[", "{"];
      let rightBracketsList = [")", "）", "]", "}"];
      let BracketsDic = {
        "(": ")",
        "（": "）",
        "[": "]",
        "{": "}",
      };
      let leftBracket = null;
      let leftBracketIndex = null;
      let index = 1;

      for (let char of str) {
        // 是否左括号
        if (leftBracketsList.includes(char)) {
          // 是否已有左括号
          if (leftBracket) {
            errorMsg = `因括号不可嵌套，第${leftBracketIndex}个字符 ${leftBracket} 在匹配右括号前，不能出现第${index}个字符 ${char} `;
            break;
          } else {
            leftBracket = char;
            leftBracketIndex = index;
          }
        } else {
          // 是否右括号
          if (rightBracketsList.includes(char)) {
            // 是否已有左括号
            if (leftBracket) {
              // 是否匹配左括号
              if (BracketsDic[leftBracket] === char) {
                leftBracket = null;
                leftBracketIndex = null;
              } else {
                errorMsg = `第${leftBracketIndex}个字符 ${leftBracket} 与第${index}个字符 ${char} 不匹配`;
                break;
              }
            } else {
              errorMsg = `第${index}个字符 ${char} 前缺少左括号`;
              break;
            }
          }
        }
        index++;
      }

      if (!errorMsg) {
        if (leftBracket) {
          errorMsg = `第${leftBracketIndex}个字符 ${leftBracket} 后缺少右括号`;
        }
      }

      return errorMsg;
    },
  },
};
</script>