<p dir="auto">The Deno repl is very... well, unhelpful I'd say. Aside from the fact I can't actually run typescript in it, it also doesn't allow very basic values:</p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="&gt; {&quot;foo&quot;:&quot;bar&quot;}
error: Uncaught SyntaxError: Unexpected token ':'
► &lt;unknown&gt;:1:7
    at evaluate ($deno$/repl.ts:84:34)
    at replLoop ($deno$/repl.ts:175:13)"><pre class="notranslate"><code class="notranslate">&gt; {"foo":"bar"}
error: Uncaught SyntaxError: Unexpected token ':'
► &lt;unknown&gt;:1:7
    at evaluate ($deno$/repl.ts:84:34)
    at replLoop ($deno$/repl.ts:175:13)
</code></pre></div>
<p dir="auto">Valid javascript, valid typescript. Why is this a syntax error?</p>
<h2 dir="auto">Error / Panicked:</h2>
<p dir="auto">thread 'main' panicked at 'called <code class="notranslate">Option::unwrap()</code> on a <code class="notranslate">None</code> value', ext/flash/lib.rs:1316:42<br>
note: run with <code class="notranslate">RUST_BACKTRACE=1</code> environment variable to display a backtrace</p>
<p dir="auto">Platform: macos aarch64<br>
Version: 1.25.0<br>
Args: ["deno", "run", "--unstable", "--allow-all", "--watch", "main.js"]</p>
<div class="highlight highlight-source-js notranslate position-relative overflow-auto" dir="auto" data-snippet-clipboard-copy-content="import express from &quot;npm:express&quot;;
const app = express();

app.get(&quot;/&quot;, function (req, res) {
  res.send(&quot;Hello Express&quot;);
});

app.listen(3000);
console.log(&quot;listening on http://localhost:3000/&quot;);"><pre class="notranslate"><span class="pl-k">import</span> <span class="pl-s1">express</span> <span class="pl-k">from</span> <span class="pl-s">"npm:express"</span><span class="pl-kos">;</span>
<span class="pl-k">const</span> <span class="pl-s1">app</span> <span class="pl-c1">=</span> <span class="pl-en">express</span><span class="pl-kos">(</span><span class="pl-kos">)</span><span class="pl-kos">;</span>

<span class="pl-s1">app</span><span class="pl-kos">.</span><span class="pl-en">get</span><span class="pl-kos">(</span><span class="pl-s">"/"</span><span class="pl-kos">,</span> <span class="pl-k">function</span> <span class="pl-kos">(</span><span class="pl-s1">req</span><span class="pl-kos">,</span> <span class="pl-s1">res</span><span class="pl-kos">)</span> <span class="pl-kos">{</span>
  <span class="pl-s1">res</span><span class="pl-kos">.</span><span class="pl-en">send</span><span class="pl-kos">(</span><span class="pl-s">"Hello Express"</span><span class="pl-kos">)</span><span class="pl-kos">;</span>
<span class="pl-kos">}</span><span class="pl-kos">)</span><span class="pl-kos">;</span>

<span class="pl-s1">app</span><span class="pl-kos">.</span><span class="pl-en">listen</span><span class="pl-kos">(</span><span class="pl-c1">3000</span><span class="pl-kos">)</span><span class="pl-kos">;</span>
<span class="pl-smi">console</span><span class="pl-kos">.</span><span class="pl-en">log</span><span class="pl-kos">(</span><span class="pl-s">"listening on http://localhost:3000/"</span><span class="pl-kos">)</span><span class="pl-kos">;</span></pre></div>
<p dir="auto">On changing a bit of code (as its watching) the error happens.</p>