Question

我在nodejs中有两个功能。一个看起来像这样

function checkAdd (
  address /* : string | void */
) /* :Promise<Object[]> */ {

  var convertToLowerCase = address.toLowerCase()

    return Promise.resolve()

    .then(() => {
      var allMatch = addressesAsJson.filter((record) => record.address === convertToLowerCase)

 });

}

还有另外一个这样的功能

function saveNewAd(
  address /* :?string | void */, cb
) /* :Promise<string> */ {

  return new Promise((resolve, reject)=> {


    var checkAddress = checkAddressAvailable(address)

    var addressAvailableResult = checkAddressAvailable(address)

    var seperatedAddress = address.split(',') 
    var firstAddLine  = capitalFirstLetter(seperatedAddress[0])
    var secondAddLine = seperatedAddress[1].toUpperCase()
    var thirdAddLine =  seperatedAddress[2].toUpperCase()

    var displayAddress = firstAddLine + ',' + secondAddLine + ',' + thirdAddLine

    addressesAsJson.push({"address": address , "display" : displayAddress})    
    fs.writeFile(jsonListPath, JSON.stringify(addressesAsJson), (err) => {
      if (err) reject(err)
      resolve("New address is saved")

    })


  });
}

在saveNewAd中，我想检查allMatch长度，如果它超过0，我需要执行saveNewAd的函数体。但它不起作用。这是我试过的。请帮我解决这个问题

function saveNewAd(
  address /* :?string | void */, cb
) /* :Promise<string> */ {

  return new Promise((resolve, reject)=> {

    var results = checkAdd(address)

    if(results.length>0){

   /*same function body as above method*/

    })
    }else{
    console.log("Error")
    }

  });
}

Answer 1

您必须使用链接，即首先异步查找allMatch，然后将此值通过.then()传递给saveNewAd函数作为参数。请注意，.then()函数实际上返回了一个与原始承诺不同的新承诺。

function checkAdd (
  address /* : string | void */
) /* :Promise<Object[]> */ {

  return new Promise((resolve, reject)=> {
    var convertToLowerCase = address.toLowerCase();

    var allMatch = addressesAsJson.filter((record) => record.address);

    resolve(allMatch);
  }
}

checkAdd()
.then((allMatch) => {
   saveNewAd(address, cb, allMatch); // now you can use allMatch as an argument in this function
}
===

MDN文档：Using Promises。

如何在另一个函数中使用nodjes promise值

1 个答案: