Merge pull request #3 from pyth-network/js-dev

initial js lib

Author: evan-gray

js/.gitignore

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+node_modules
+/lib

js/.prettierrc

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+{
+  "printWidth": 120,
+  "trailingComma": "all",
+  "semi": false,
+  "singleQuote": true
+}

js/README.md

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+# pyth-client
+
+## A library for parsing on-chain Pyth oracle data
+
+[Pyth](https://pyth.network/) is building a way to deliver a decentralized, cross-chain market of verifiable data from high-quality nodes to any smart contract, anywhere.
+
+This library consumes on-chain Pyth `accountInfo.data` from [@solana/web3.js](https://www.npmjs.com/package/@solana/web3.js) and returns JavaScript-friendly objects.
+
+See our [examples repo](https://github.com/pyth-network/pyth-examples) for real-world usage examples.
+
+## Example Usage
+
+```
+import { Connection, PublicKey } from '@solana/web3.js'
+import { parseMappingData, parsePriceData, parseProductData } from '@pythnetwork/pyth-client'
+const connection = new Connection(SOLANA_CLUSTER_URL)
+  const publicKey = new PublicKey(ORACLE_MAPPING_PUBLIC_KEY)
+  connection.getAccountInfo(publicKey).then((accountInfo) => {
+    const { productAccountKeys } = parseMappingData(accountInfo.data)
+    connection.getAccountInfo(productAccountKeys[productAccountKeys.length - 1]).then((accountInfo) => {
+      const { product, priceAccountKey } = parseProductData(accountInfo.data)
+      connection.getAccountInfo(priceAccountKey).then((accountInfo) => {
+        const { price, confidence } = parsePriceData(accountInfo.data)
+        console.log(`${product.symbol}: $${price} \xB1$${confidence}`)
+        // SRM/USD: $8.68725 ±$0.0131
+      })
+    })
+  })
+```
+
+To get streaming price updates, you may want to use `connection.onAccountChange`

js/jestconfig.json

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+{
+  "transform": {
+    "^.+\\.(t|j)sx?$": "ts-jest"
+  },
+  "testRegex": "(/__tests__/.*|(\\.|/)(test|spec))\\.(jsx?|tsx?)$",
+  "moduleFileExtensions": ["ts", "tsx", "js", "jsx", "json", "node"]
+}