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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>JavaScript Playground</title>
<meta name="description" content="A JavaScript jungle-gym for doing experiments and sharing scrappy fiddles.">
<style>
html, body { height: 100%; margin: 0; padding: 0; }
body { display: flex; flex-direction: column; background-color: #ddd; }
#app { display: flex; flex-direction: column; padding: 10px; height: 100%; box-sizing: border-box; }
.button-container { width: 100%; display: flex; justify-content: flex-end; margin-bottom: 10px; flex-shrink: 0; }
button { padding: 10px 20px; font-size: 1rem; margin-left: 10px; cursor: pointer; border: none; transition: background-color 0.3s ease; }
button:hover, button:focus { outline: none; }
button:disabled { background-color: #999; cursor: not-allowed; }
button.run { background-color: teal; color: #FFFFFF; }
textarea { width: 100%; height: 64%; font-family: monospace; background-color: #FFFEEC; border: 2px solid #000; scrollbar-width: none; font-size: 1rem; margin-bottom: 10px; padding: 10px; box-sizing: border-box; resize: none; border-bottom: 12px solid teal; -webkit-user-modify: read-write-plaintext-only; flex-shrink: 0; }
textarea::-webkit-scrollbar { display: none; }
textarea::selection { background-color: #EFECA7; }
textarea:focus { outline: none; }
#console { width: 100%; height: 22%; background-color: #000; color: #0fc; font-family: monospace; font-size: 1rem; overflow-y: auto; padding: 10px; box-sizing: border-box; white-space: pre-wrap; flex-grow: 1; }
#console .log-item { margin-bottom: 5px; border-bottom: 1px solid #333; }
#console details { cursor: pointer; }
#console summary { outline: none; }
</style>
</head>
<body>
<div id="app"></div>
<iframe id="sandbox" style="display: none;" title="JavaScript Sandbox"></iframe>
<script>
/**
* ----------------------------------------------------------------
* Functional Utilities
* ----------------------------------------------------------------
*/
const pipe = (...fns) => (initialValue) => fns.reduce((acc, fn) => fn(acc), initialValue);
const compose = (...fns) => (initialValue) => fns.reduceRight((acc, fn) => fn(acc), initialValue);
/**
* ----------------------------------------------------------------
* The Elm Architecture (Model, View, Update) Implementation
* ----------------------------------------------------------------
*/
const init = {
code: `
const add = (a, b) => a + b;
const multiply = (a, b) => a * b;
const addAndMultiply = pipe(add, multiply);
console.log(addAndMultiply(2, 3));
`,
consoleOutput: [],
sandboxReady: false,
};
const view = (model) => `
<div class="button-container">
<button onclick="dispatch({ type: 'CLEAR' })">Clear</button>
<button onclick="dispatch({ type: 'DOWNLOAD' })">Download</button>
<button onclick="dispatch({ type: 'SHARE' })">Share</button>
<button onclick="dispatch({ type: 'RUN_CODE' })" class="run" ${!model.sandboxReady ? 'disabled title="Sandbox is loading..."' : ''}>Run Code</button>
</div>
<textarea id="codeInput" oninput="dispatch({ type: 'CODE_CHANGED', payload: this.value })" onkeydown="handleKeyDown(event)">${model.code}</textarea>
<div id="console">
${model.consoleOutput.map(log => {
if (typeof log === 'object' && log !== null) {
return `<div class="log-item"><details><summary>${Object.prototype.toString.call(log)}</summary><pre>${JSON.stringify(log, null, 2)}</pre></details></div>`;
}
return `<div class="log-item">${log}</div>`;
}).join('')}
</div>
`;
const update = (msg, model) => {
switch (msg.type) {
case 'CODE_CHANGED':
return { ...model, code: msg.payload };
case 'RUN_CODE':
return model;
case 'CONSOLE_LOG':
return { ...model, consoleOutput: [...model.consoleOutput, ...msg.payload] };
case 'CLEAR':
if (confirm('Are you sure you want to reset the playground?')) {
window.location.hash = '';
window.location.reload();
}
return model;
case 'CLEAR_CONSOLE':
return { ...model, consoleOutput: [] };
case 'SHARE':
case 'DOWNLOAD':
return model;
case 'SANDBOX_READY':
return { ...model, sandboxReady: true };
default:
return model;
}
};
/**
* ----------------------------------------------------------------
* Application Core & Side-Effect Handling
* ----------------------------------------------------------------
*/
let model = null;
const appContainer = document.getElementById('app');
const sandbox = document.getElementById('sandbox');
const dispatch = (msg) => {
const newModel = update(msg, model);
handleSideEffects(msg, newModel);
model = newModel;
render(model);
};
const handleSideEffects = (msg, model) => {
if (msg.type === 'RUN_CODE') {
if (!model.sandboxReady) return;
dispatch({ type: 'CLEAR_CONSOLE' });
sandbox.contentWindow.postMessage({ code: model.code }, '*');
} else if (msg.type === 'SHARE') {
const encodedCode = btoa(encodeURIComponent(model.code));
window.location.hash = encodedCode;
window.prompt("Copy the URL to share.", window.location.href);
} else if (msg.type === 'DOWNLOAD') {
const htmlContent = document.documentElement.outerHTML.replace(
/<textarea id="codeInput"[^>]*>.*<\/textarea>/,
`<textarea id="codeInput">${model.code}</textarea>`
);
const blob = new Blob([htmlContent], { type: 'text/html' });
const url = URL.createObjectURL(blob);
const a = document.createElement('a');
a.href = url;
a.download = 'playground.html';
a.click();
URL.revokeObjectURL(url);
}
};
const render = (model) => {
const focusedElementId = document.activeElement?.id;
const selectionStart = document.activeElement?.selectionStart;
const selectionEnd = document.activeElement?.selectionEnd;
appContainer.innerHTML = view(model);
if (focusedElementId === 'codeInput') {
const focusedElement = document.getElementById(focusedElementId);
if (focusedElement) {
focusedElement.focus();
if (typeof selectionStart === 'number') {
focusedElement.selectionStart = selectionStart;
focusedElement.selectionEnd = selectionEnd;
}
}
}
};
const handleKeyDown = (event) => {
if (event.key === 'Tab') {
event.preventDefault();
const start = event.target.selectionStart;
const end = event.target.selectionEnd;
event.target.value = event.target.value.substring(0, start) + " " + event.target.value.substring(end);
dispatch({ type: 'CODE_CHANGED', payload: event.target.value });
event.target.selectionStart = event.target.selectionEnd = start + 2;
}
if (event.metaKey && event.key === 'Enter') {
event.preventDefault();
dispatch({ type: 'RUN_CODE' });
}
};
/**
* ----------------------------------------------------------------
* Sandbox Initialization
* ----------------------------------------------------------------
*/
const sandboxSrc = `
<script>
const pipe = ${pipe.toString()};
const compose = ${compose.toString()};
const originalConsoleLog = console.log;
console.log = (...args) => {
parent.postMessage({ type: 'CONSOLE_LOG', payload: args }, '*');
};
window.addEventListener('message', (event) => {
try {
eval(event.data.code);
} catch (e) {
console.log(e.toString());
}
});
<\/script>
`;
window.addEventListener('message', (event) => {
if (event.source === sandbox.contentWindow && event.data.type === 'CONSOLE_LOG') {
dispatch(event.data);
}
});
/**
* ----------------------------------------------------------------
* Application Entry Point
* ----------------------------------------------------------------
*/
const hash = window.location.hash.substring(1);
if (hash) {
try {
const decodedCode = decodeURIComponent(atob(hash));
model = { ...init, code: decodedCode };
} catch (error) {
console.error('Failed to decode the URL hash:', error);
model = init;
}
} else {
model = init;
}
render(model);
sandbox.onload = () => {
dispatch({ type: 'SANDBOX_READY' });
};
sandbox.srcdoc = sandboxSrc;
</script>
</body>
</html>
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