Node.js中因PM2不支持可选链，转换判断逻辑遇问题求助

原代码使用可选链操作符（?.）能正确匹配销售记录，但转换为旧版判断逻辑后无法输出“purchase has been SOLD.”，问题出在转换后的判断逻辑错误。

原工作代码 #

// Working solution
purchases.forEach((purchase) => {
  const matchingItems = sales.filter(obj => obj.elements[0]?.specialId === purchase.elements[0]?.specialId);
  if (matchingItems.length > 0){
   console.log('purchase has been SOLD.')
    purchase.sold = true
  }
})

转换后失效的代码 #

purchases.forEach((purchase) => {
    // const matchingItems = sales.filter(obj => obj.elements[0] && obj.elements[0].specialId === purchase.elements[0] && purchase.elements[0].specialId);

    const matchingItems = sales.filter((obj) => {
        return obj.elements[0] && obj.elements[0].specialId === purchase.elements[0] && purchase.elements[0].specialId
    })

    if (matchingItems.length > 0){
        console.log('purchase has been SOLD.')
        purchase.sold = true
    }
})

错误原因分析 #

原可选链的逻辑是：当obj.elements[0]存在时取其specialId，否则为undefined；同时当purchase.elements[0]存在时取其specialId，否则为undefined，最后判断这两个值是否相等。

但转换后的代码逻辑完全偏离：由于===的优先级高于&&，实际执行顺序变成了obj.elements[0] && (obj.elements[0].specialId === purchase.elements[0]) && purchase.elements[0].specialId——这相当于把obj.elements[0].specialId和purchase.elements[0]对象本身做比较，而非比较两者的specialId；同时后面多余的purchase.elements[0].specialId会在值为假时（比如0、空字符串）导致整个条件不成立。

正确的转换代码 #

需要先分别处理两边的specialId取值逻辑，再做相等判断，和原可选链逻辑保持一致：

写法一（兼容性更强，适合specialId可能为假值的场景） #

purchases.forEach((purchase) => {
    const matchingItems = sales.filter((obj) => {
        // 明确获取两边的specialId，不存在则为undefined
        const objSpecialId = obj.elements[0] ? obj.elements[0].specialId : undefined;
        const purchaseSpecialId = purchase.elements[0] ? purchase.elements[0].specialId : undefined;
        return objSpecialId === purchaseSpecialId;
    })

    if (matchingItems.length > 0){
        console.log('purchase has been SOLD.')
        purchase.sold = true
    }
})

写法二（更紧凑，适合specialId始终为真值的场景） #

purchases.forEach((purchase) => {
    const matchingItems = sales.filter((obj) => {
        return (obj.elements[0] && obj.elements[0].specialId) === (purchase.elements[0] && purchase.elements[0].specialId);
    })

    if (matchingItems.length > 0){
        console.log('purchase has been SOLD.')
        purchase.sold = true
    }
})

内容的提问来源于stack exchange，提问作者TC23