@parity/light.js
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A high-level reactive JS library optimized for light clients
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Tutorial Part 3: Manipulating RpcObservables
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FrequencyObservables
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RpcObservables
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MakeContract
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rpc/rpc
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rpc/utils/createRpc
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FrequencyObservable
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MakeContract
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RpcObservable
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RpcObservableOptions
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TxStatus
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Utils
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utils/isLoading
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<h1 id="tutorial-part-3-manipulating-rpcobservables">Tutorial Part 3: Manipulating RpcObservables</h1>
<h2 id="operators-on-observables">Operators on Observables</h2>
<p>Since <code>@parity/light.js</code> relies heavily on RxJS Observables, all the tools for playing with Observables are available for you to use.</p>
<h3 id="format-the-balance-nicely">Format the balance nicely</h3>
<pre><code class="lang-javascript"><span class="hljs-keyword">import</span> { map } <span class="hljs-keyword">from</span> <span class="hljs-string">'rxjs/operators'</span>;
balanceOf$(<span class="hljs-string">'0x407d73d8a49eeb85d32cf465507dd71d507100c1'</span>)
.pipe( <span class="hljs-comment">// We can chain operators</span>
map(balance => balance.toFormat(<span class="hljs-number">2</span>)), <span class="hljs-comment">// Format the number nicely</span>
map(balance => <span class="hljs-string">`<span class="hljs-subst">${balance}</span> ETH`</span>) <span class="hljs-comment">// Append 'ETH'</span>
)
.subscribe(balance => <span class="hljs-built_in">console</span>.log(<span class="hljs-string">'balance'</span>, balance));
<span class="hljs-comment">// Logs:</span>
<span class="hljs-comment">// balance 2,000.00 ETH</span>
<span class="hljs-comment">// ...</span>
</code></pre>
<p>See <a href="https://codesandbox.io/s/xp87z0xjmo" target="_blank">https://codesandbox.io/s/xp87z0xjmo</a>.</p>
<h3 id="only-log-pair-block-numbers">Only log pair block numbers</h3>
<pre><code class="lang-javascript"><span class="hljs-keyword">import</span> { map, filter } <span class="hljs-keyword">from</span> <span class="hljs-string">'rxjs/operators'</span>;
blockNumber$()
.pipe(
map(v => +v), <span class="hljs-comment">// Convert BigNumber to number</span>
filter(blockNumber => blockNumber % <span class="hljs-number">2</span> === <span class="hljs-number">0</span>) <span class="hljs-comment">// Filter out pair numbers</span>
)
.subscribe(blockNumber => <span class="hljs-built_in">console</span>.log(<span class="hljs-string">'blockNumber'</span>, blockNumber)); <span class="hljs-comment">// Same as before, log the result</span>
<span class="hljs-comment">// Logs:</span>
<span class="hljs-comment">// blockNumber 8548408</span>
<span class="hljs-comment">// blockNumber 8548410</span>
<span class="hljs-comment">// ...</span>
</code></pre>
<p>See <a href="https://codesandbox.io/s/v37j38o38y" target="_blank">https://codesandbox.io/s/v37j38o38y</a>.</p>
<h3 id="get-the-balance-of-the-current-account">Get the balance of the current account</h3>
<pre><code class="lang-javascript">defaultAccount$()
.pipe(
switchMap(publicAddress => balanceOf$(publicAddress)),
map(value => +value) <span class="hljs-comment">// Return number instead of BigNumber</span>
)
.subscribe(<span class="hljs-built_in">console</span>.log);
<span class="hljs-comment">// Logs:</span>
<span class="hljs-comment">// 2</span>
<span class="hljs-comment">// ...</span>
</code></pre>
<h3 id="conclusion">Conclusion</h3>
<p>RxJS has <a href="http://reactivex.io/documentation/operators.html" target="_blank">a lot of operators</a> which you can use to combine the RpcObservables to build your app's logic. <code>@parity/light.js</code> provides the basic RpcObservables, and we let you combine them.</p>
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