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How to create an English auction on a marketplace

Prerequisites​

Before getting started, make sure you have the following ready:

  1. Create a Ternoa account with Alphanet CAPS
  2. Install and set up your editor of choice (we will use Visual Studio Code [VSC] in this tutorial)
  3. Install NodeJS v.14+ & NPM
  4. Install & initialize Ternoa-JS

Create an auction on a marketplace using Ternoa-JS​

This function put an existing NFT to auction on a marketplace on the Ternoa chain. It returns an object promise containing the AuctionCreatedEvent provided by the Ternoa blockchain.

info

Use your own account by updating the //TernoaTestAccount with your account seed when retrieving the keyring from the example below. Replace the NFT_ID with the existing one to aution, the MARKETPLACE_ID by the existing marketplace id you want the NFT to be auctioned on, the startBlock, endBlock, startPrice, buyItPrice.

import {
    createAuction,
    initializeApi,
    getKeyringFromSeed,
    WaitUntil,
} from "ternoa-js";

const listAuctionNFT = async () => {
    try {
        await initializeApi();
        const keyring = await getKeyringFromSeed("//TernoaTestAccount");
        const NFT_ID = // update with the nft id you want to put in auction.
        const MARKETPLACE_ID = // update with the marketplace id you want the NFT to be auctioned on.
        const startBlock = // update with the auction start block number.
        const endBlock = // update with the auction end block number.
        const startPrice = // update with the auction start price.
        const buyItPrice = // update with the auction "buy it now" price.
        const res = await createAuction(
            NFT_ID,
            MARKETPLACE_ID,
            startBlock,
            endBlock,
            startPrice,
            buyItPrice,
            keyring,
            WaitUntil.BlockInclusion
        );
        console.log(`NFT id: ${res.nftId} auctioned on marketplace ${res.marketplaceId} for ${res.startPrice}CAPS`);
    } catch (e) {
        console.error(e);
    }
};

The expected params​

`nftId`: The ID of the NFT.
`marketplaceId`: The ID of the marketplace where the auction will take place.
`startBlock`: The ID of the block at which the auction starts.
`endBlock`: The ID of the block at which the auction ends.
`startPrice`: The price at which the auction starts.
`buyItPrice`: The price to directly buy the NFT before the auction starts. Optional Parameter.
`keyring`: The provided keyring (containing the address) will be used to sign the transaction and pay the execution fee.
`waitUntil`: WaitUntil define at which point we want to get the results of the transaction execution: BlockInclusion or BlockFinalization.

Response​

The response provided from the blockchain event includes all the informations below according to the params provided when buying an NFT.

`nftId`: NFT id auctioned.
`marketplaceId`: Marketplace id where the NFT was listed for auction.
`creator`: The auction creator.
`startPrice`: The starting auction price of the NFT as a string corresponding to the value in big number.
`startPriceRounded`: The starting auction price of the NFT as number.
`buyItPrice`: If set, the price to directly buy the NFT before the auction starts as a string corresponding to the value in big number.
`buyItPriceRounded`: If set, The price to directly buy the NFT before the auction starts as number.
`startBlock`: The aution starting block number.
`endBlock`: The aution ending block number.

Support​

If you face any trouble, feel free to reach out to our community engineers in our Discord.