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Your first Prep query

Try the playground first

Open Prep Playground to choose an example, select fields and run a public testnet query in your browser.

Fetch Zcash block headers with the JavaScript client. This example reads testnet blocks 0 and 1 and prints the selected fields.

Prerequisites​

Node.js 22.18+ and pnpm, or npm using the alternative below. The public testnet preview requires no personal API token.

1. Install the client​

mkdir prep-quickstart
cd prep-quickstart
npm init -y
pnpm add @zeer-dev/prep-client@0.1.0

With npm, use npm install @zeer-dev/prep-client@0.1.0 instead.

2. Write your query​

Save this as read-blocks.mjs:

import { PrepClient } from "@zeer-dev/prep-client";

const client = new PrepClient({ url: "https://zeer.endpx.cloud/api/prep" });
const coverage = await client.getHeight();
if (!coverage.ready || coverage.start_block > 0 ||
    coverage.indexed_height === null || coverage.indexed_height < 1) {
  throw new Error("Blocks 0 and 1 are not available from this source.");
}

const query = {
  from_block: 0,
  to_block: 2,
  field_selection: { block: ["height", "hash", "time"], transaction: [] },
};

for await (const page of client.stream(query)) {
  console.log(page.data.blocks);
}

3. Run​

node read-blocks.mjs

The output contains block heights 0 and 1, each with its hash and timestamp. to_block is exclusive, so 2 is outside the requested range.

How it works​

PartPurpose
PrepClientConnects to the chosen network URL
getHeight()Checks available coverage and readiness
field_selectionReturns only the fields you request; transaction: [] omits transaction records
stream(query)Follows response cursors until the captured range is complete

Next steps​