In order and In Sync (high performance) JS

speed.js

// Immediate execution, for of with indexes, in order
const r = ["a",2,3,4,5]
const t = (i) => {
    return new Promise((resolve, reject) => {
        setTimeout(() => {
            resolve(`hi ${i}`)
        }, 1000 * i)
    })
}

!async function() {
    for(const [i, e] of r.entries()) {
        const q = await t(1)
        console.log(e, q)
    }
}()

(async () => {
  /* */
})()


// Run async with sync inside

const po = () => {
    return new Promise((resolve, reject) => {
        setTimeout(() => {
            resolve("hi")
        }, 2000)
    })
}

const zz = ["hey", "hi", "ho"]

await Promise.all(zz.map(async (ele) => {
    const y = await po()
    console.log(y)
    return ele
}))
.then((balues) => {
    console.log(balues)
    for (val of balues) {
        console.log('eee')
    }
})

// Similar to above:
// Upload step images
  const stepimageProms = []
  const stepimageArr = Array(this.state.steps.length)
  for (let i = 0; i < this.state.steps.length; i++) {
    if (this.state.steps[i].image) {
      const fileName = `images/${uuid()}-${this.state.steps[i].image.name}`
      const imageRef = storageRef.child(fileName)
      await stepimageProms.push(
        await imageRef.put(this.state.steps[i].image)
        .then(async (uploadSnap) => {
          const downloadURL = await imageRef.getDownloadURL()
          stepimageArr[i] = downloadURL
        })
          .catch((e) => {
            console.error('Error uploading step iomage:')
            console.error(e)
          })
      )
    }
  }
  // Handle steps
  Promise.all(stepimageProms)
    .then(() => {})

// Manual delay of impossible async stuff:
!function(){
    for (const [i, e] of r.entries()) {
        setTimeout(() => {
            // some impossible async thing that await is just not working on
            console.log(e)
        }, 1000*i) // maunally delay firing it off
    }
}()


// Batching groups of promises for doing large arrays of promises quickly in groups of 10
let final = []
let batch = []
for (let i = 0; i<devices.length + 11; i++) { // make sure we get them all
    const dev = devices[i]
    if (i%10 == 0 && i > 1) {
        batch.push(dev) // don't skip every 10
        console.log("doing 10")
        await Promise.all(batch.map(async (ele) => { // async inside so we've read before we return
            console.log("doing the lords work")
            await db.collection("clients").doc(cuid).collection("devices").doc(ele).get()
            .then((docSnap) => {
                let infoObj = docSnap.data()
                infoObj.duid = ele
                final.push(infoObj)
            })
            .catch((err) => {
                console.error("Error getting devices from campaign")
                console.error(err)
                reject(err)
            })
            return (ele)
        }))
        console.log("did 10:")
        batch = [] // clear the batch
    } else {
        batch.push(dev)
    }
}