判断字符串是不是正则表达式

    
   :rules="[
            { required: true, trigger: 'blur', validator: this.checkCanonical },
          ]"

checkCanonical (rule, value, callback) {
      if (value) {
        let isReg = true
        try {
          isReg = eval(value) instanceof RegExp
        } catch (e) {
          isReg = false
        }
        isReg ? callback() : callback(new Error('请输入正确的正则表达式'))
      } else {
        callback(new Error('请输入正则表达式'))
      }
    },