如何循环遍历 mongoose id 数组以检查它是否有效并且它确实存在于数据库中，然后推送到一个新数组

Question

The function loops through an array from the request body and checks if the productId property is valid if it's valid I push to a new array existingProductId, but it ends up returning an empty array. Please any ideas or solution.

 function returnValidId(products){
 var existingProductId = [];
 products.map(async(product)=>{
 const existingProduct = await Product.findById(product.productId)
 if(existingProduct){
  existingProductId.push({id:existingProduct._id})
 }
 })
 return existingProductId;
 }
 const data = returnValidId(products)
 console.log(data)

Answer 1

You are using .map and you are returning promises, but you are not waiting the resolve of those promises and the function returns the empty array. Try:

async function returnValidId(products){
  var existingProductId = [];
  await Promise.all(products.map(async(product)=>{
    const existingProduct = await Product.findById(product.productId)
    if(existingProduct){
      existingProductId.push({id:existingProduct._id})
    }
  }));
  return existingProductId;
 }
 const data = await returnValidId(products)
 console.log(data)

With Promise.all you are waiting for the promises to be resolved.