1. The meaning of the |

| in vue is a pipe symbol, the front to the value of the filter for you, followed by a filter, a filter is after you filter value. For example: : placeholder = “item | placeholder ()” placeholder () is a filter.

 filters: {
      placeholder(item,value) {
        if (value === 'select') {
          return item.placeholder ? item.placeholder : 'Please select'+ item.label
        } else if (value === 'date') {
          return item.placeholder ? item.placeholder : 'Please select the time'
        }else {
          return item.placeholder ? item.placeholder : 'Please enter'+ item.label
        }
      },
      defaultValue(item, value) {
        returnitem ! = =undefined ? item : value
      }
    }
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2. | | meaning: | | is or relationship between conditions.