Lesson 14: 'fileIndex' is nowhere declared in uploadToPinata.js

[ManuWeb3]

Hi all,

How come we're able to use the variable fileIndex without declaring it anywhere inside uploadToPinata.js below ?

Is it some kind of an in-built identifier ?

I tried to console.log(fileIndex) before using it inside for () loop, it threw below error but when directly used inside the for() loop, it works fine. How ?

uploadToPinata.js

const pinataSDK = require("@pinata/sdk")
const fs = require("fs")
const path = require("path")

const pinataApiKey = process.env.PINATA_API_KEY || ""
const pinataApiSecret = process.env.PINATA_API_SECRET || ""
const pinata = pinataSDK(pinataApiKey, pinataApiSecret)

async function storeImages(imagesFilePath) {
    const fullImagesPath = path.resolve(imagesFilePath)
    const files = fs.readdirSync(fullImagesPath)
    let responses = []
    for (fileIndex in files) {
        const readableStreamForFile = fs.createReadStream(`${fullImagesPath}/${files[fileIndex]}`)
        try {
            const response = await pinata.pinFileToIPFS(readableStreamForFile)
            responses.push(response)
        } catch (error) {
            console.log(error)
        }
    }
    return { responses, files }
}

async function storeTokenUriMetadata(metadata) {
    try {
        const response = await pinata.pinJSONToIPFS(metadata)
        return response
    } catch (error) {
        console.log(error)
    }
    return null
}

module.exports = { storeImages, storeTokenUriMetadata }

[RoboCrypter]

@ManuWeb3 : We are using fileIndex as an index in files. So, that's why we are saying it like fileIndex in files,

We are using in, Because we want it to loop to all the files, Its the JS for - in Loops It Loops the properties of an object

And because of this outside for loop in does not work.

[ManuWeb3]

Hey @abossofmyself , thanks for the quick reply. Got it now.

My knowledge of JS is only limited to what Patrick taught during the course of this tutorial.
However, I have plans to learn full-blown JS and TS once I'm done with this course.

[RoboCrypter]

@ManuWeb3 Awesome! Thats great

Have a good one!