javascript - Filtered.push 不是一个函数

Question

我正在使用reduce函数，由于某种原因我在控制台上收到错误:

(index):77 Uncaught TypeError: filtered.push is not a function

DispatchedNumber 在映射到 Lines 数组之前应该存在。

function payload(order) {
  return {
    OrderId: order.ORDERID,
    Lines: order.ITEMS.reduce(function(filtered, item) {
      if (item.DispatchedNumber != undefined) {
        var newItem = {
          Qty: item.Qty,
          QtyShipped: item.DispatchedNumber
        }

        filtered.push(newItem);
      }

      return filtered;
    })
  }
}

test = payload({
  "ORDERID": 1233,
  "ITEMS": [
    { Qty: 123, DispatchedNumber: 111 },
    { Qty: 111 },
    { Qty: 444, DispatchedNumber: 555 },
    { Qty: 443, DispatchedNumber: 323 }
  ]
})

用法:

console.log(JSON.stringify(test, null, 2));

示例:https://jsfiddle.net/j6097w9d/2/

Answer 1

reduce 函数中没有为累加器指定初始值。

请更新以下内容

order.ITEMS.reduce(function(filtered, item) {
      if (item.DispatchedNumber != undefined) {
        var newItem = {
          Qty: item.Qty,
          QtyShipped: item.DispatchedNumber
        }

        filtered.push(newItem);
      }

      return filtered;
    }, []) // add the empty array (initial value of accumulator)

供引用，Array.reduce