<p>๋น„๋™๊ธฐ ํ•จ์ˆ˜๊ฐ€ ์ฃผ์–ด์ง€๋ฉด async.waterfall์ด ์ค‘๋‹จ๋ฉ๋‹ˆ๋‹ค (๋…ธ๋“œ 8).</p>

์— ๋งŒ๋“  2017๋…„ 10์›” 05์ผ  ยท  8์ฝ”๋ฉ˜ํŠธ  ยท  ์ถœ์ฒ˜: caolan/async

์–ด๋–ค ๋ฒ„์ „์˜ ๋น„๋™๊ธฐ๋ฅผ ์‚ฌ์šฉํ•˜๊ณ  ์žˆ์Šต๋‹ˆ๊นŒ?
2.5.0

(๋…ธ๋“œ ๋ฒ„์ „ / ๋ธŒ๋ผ์šฐ์ € ๋ฒ„์ „)์—์„œ ๋ฌธ์ œ๊ฐ€ ๋ฐœ์ƒํ•œ ํ™˜๊ฒฝ
๋…ธ๋“œ 8

๋ญ ํ–ˆ์–ด?

async=require('async')

async function myFirstFunction(callback) {
     callback(null, 'one', 'two');
}

function mySecondFunction(arg1, arg2, callback) {
     // arg1 now equals 'one' and arg2 now equals 'two'
     callback(null, 'three');
}

async function myLastFunction(arg1, callback) {
     // arg1 now equals 'three'
     callback(null, 'done');
}

async.waterfall([
     myFirstFunction,
     mySecondFunction,
     myLastFunction,
], function (err, result) {
     // result now equals 'done'
     console.log(err, result)
});

๋ฌด์Šจ ์ผ์ด ์ผ์–ด๋‚˜๊ธฐ๋ฅผ ๊ธฐ๋Œ€ ํ–ˆ์Šต๋‹ˆ๊นŒ?
์˜ˆ์™ธ๊ฐ€ ์—†๋‹ค

์‹ค์ œ ๊ฒฐ๊ณผ๋Š” ๋ฌด์—‡์ž…๋‹ˆ๊นŒ?

> TypeError: callback is not a function
    at myFirstFunction (repl:2:5)
    at /Users/scott/node_modules/async/dist/async.js:143:27
    at /Users/scott/node_modules/async/dist/async.js:21:12
    at nextTask (/Users/scott/node_modules/async/dist/async.js:5297:14)
    at Object.waterfall (/Users/scott/node_modules/async/dist/async.js:5307:5)
    at repl:1:7
    at ContextifyScript.Script.runInThisContext (vm.js:44:33)
    at REPLServer.defaultEval (repl.js:239:29)
    at bound (domain.js:301:14)
    at REPLServer.runBound [as eval] (domain.js:314:12) undefined
docs question

๊ฐ€์žฅ ์œ ์šฉํ•œ ๋Œ“๊ธ€

์˜ˆ, ๋‹ค์Œ๊ณผ ๊ฐ™์ด ํ•  ์ˆ˜ ์žˆ์Šต๋‹ˆ๋‹ค.

async.waterfall([
  // ...
  async function (arg1, arg2) {
    //...
    const arg3 = await foo()
    return [arg1, arg2, arg3]
  },
  function ([arg1, arg2, arg3], callback) {
    //...
  }

๋ชจ๋“  8 ๋Œ“๊ธ€

์ฝœ๋ฐฑ์€ async ํ•จ์ˆ˜์— ์ „๋‹ฌ๋˜์ง€ ์•Š๊ณ  ๋Œ€์‹  ๊ฐ’์„ ๋ฐ˜ํ™˜ํ•ฉ๋‹ˆ๋‹ค.

myFirstFunction callback ์— ๋‘˜ ์ด์ƒ์˜ ์ธ์ˆ˜๊ฐ€ ์ „๋‹ฌ๋˜๋Š” ์œ„์˜ ์ฒซ ๋ฒˆ์งธ ํ•จ์ˆ˜์˜ ๊ฒฝ์šฐ ๋Œ€์‹  ๋ฐฐ์—ด์„ ๋ฐ˜ํ™˜ํ•ด์•ผํ•ฉ๋‹ˆ๊นŒ?

์˜ˆ, ๋‹ค์Œ๊ณผ ๊ฐ™์ด ํ•  ์ˆ˜ ์žˆ์Šต๋‹ˆ๋‹ค.

async.waterfall([
  // ...
  async function (arg1, arg2) {
    //...
    const arg3 = await foo()
    return [arg1, arg2, arg3]
  },
  function ([arg1, arg2, arg3], callback) {
    //...
  }

๊ทธ๋ ‡๋‹ค๋ฉด ์˜ค๋ฅ˜๋ฅผ ๋ฐ˜ํ™˜ํ•˜๋Š” ๋ฐฉ๋ฒ•์€ ๋ฌด์—‡์ž…๋‹ˆ๊นŒ? ๊ทธ๋ƒฅ ๋˜์ ธ?

์œ„์˜ ์งˆ๋ฌธ์— ๋Œ€ํ•œ ๋‹ต์ด ์žˆ์Šต๋‹ˆ๊นŒ? ๋‚˜๋Š” ๋น„๋™๊ธฐ ํ•จ์ˆ˜์—์„œ ์˜ค๋ฅ˜๊ฐ€ ๋ฐœ์ƒํ–ˆ์„ ๋•Œ ๋ณด์„๊ธˆ์„ ๋‚ด๊ฒ ๋‹ค๊ณ  ๋ฏฟ์Šต๋‹ˆ๋‹ค. ์—ฌ์ „ํžˆ "next"์ฝœ๋ฐฑ์„ ํ˜ธ์ถœํ•ด์•ผํ•ฉ๋‹ˆ๋‹ค.

์ด๊ฑด ์–ด๋•Œ์š”?

async.waterfall([
  // ...
  async function (arg1, arg2, callback) {
    //...
    try {
      const arg3 = await foo()
      return [arg1, arg2, arg3]
    } catch (err) {
      callback('An error occured:' + err.message);
    }
  },
  function ([arg1, arg2, arg3], callback) {
    //...
  }

async ํ•จ์ˆ˜๋Š” ์ „๋‹ฌ ๋œ ์ฝœ๋ฐฑ์„๋ฐ›์ง€ ์•Š์Šต๋‹ˆ๋‹ค. throw ์˜ค๋ฅ˜์ž…๋‹ˆ๋‹ค.

๊ฐ์‚ฌ.

์ด ํŽ˜์ด์ง€๊ฐ€ ๋„์›€์ด ๋˜์—ˆ๋‚˜์š”?
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