rileyjshaw/bracket-parse.js

## bracket-parse.js
/**
 * Parse takes a string and returns a nested array. The array nests
 * to a deeper level for each [[enclosed double bracket pair]].
 *
 * eg:
 *
 *   // Output: ['It goes ', ['deeper and ', ['deeper.']]]
 *   parse('It goes [[deeper and [[deeper.]]]]');
 */
function parse(str, startIdx = 0, isChild = false) {
	const result = [];
	for (let i = startIdx + 1, _len = str.length; i < _len; ++i) {
		const char = str[i];
		let isOpen = false,
			isClosed = false;
		if (char === str[i - 1]) {
			if (char === '[') isOpen = true;
			else if (char === ']') isClosed = true;
		}
		if (isOpen || isClosed) {
			// Ensure the possible substring between the prior token and here is captured.
			if (i > startIdx + 1) result.push(str.slice(startIdx, i - 1));
			if (isOpen) {
				const [contents, nextIdx] = parse(str, i + 1, true);
				result.push(contents);
				i = startIdx = nextIdx;
			} else if (isClosed) {
				return isChild ? [result, i + 1] : result;
			}
		}
	}
	if (str.length !== startIdx) result.push(str.slice(startIdx, str.length));
	return isChild ? [result, str.length] : result;
}

// Tests below here.
const testCases = [
	['A simple string', ['A simple string']],
	['A simple string [ [ [][][] ] ] with single brackets', ['A simple string [ [ [][][] ] ] with single brackets']],
	['[[An enclosed string]]', [['An enclosed string']]],
	['[[Each]][[word]][[separately]][[enclosed]]', [['Each'], ['word'], ['separately'], ['enclosed']]],
	['[[Some words are enclosed]] but some are not', [['Some words are enclosed'], ' but some are not']],
	[
		'This [[[[is a test]] of some nested groups]] and the [[resulting]] data structure [[should [[be [[nested]] accordingly]]]]',
		[
			'This ',
			[['is a test'], ' of some nested groups'],
			' and the ',
			['resulting'],
			' data structure ',
			['should ', ['be ', ['nested'], ' accordingly']],
		],
	],
	['This: ]] will close early…', ['This: ']],
	['This: [[[[[[ will close at the end…', ['This: ', [[[' will close at the end…']]]]],
	['This will have an empty array at the end: [[', ['This will have an empty array at the end: ', []]],
	['', []],
];
// Util.
function miniDeepArrayCompare(array1, array2) {
	return (
		Array.isArray(array2) &&
		array1.length === array2.length &&
		array1.every((a, i) => {
			const b = array2[i];
			return Array.isArray(a) ? miniDeepArrayCompare(a, b) : a === b;
		})
	);
}
const results = testCases.map(([str, expectedResult]) => miniDeepArrayCompare(parse(str), expectedResult));
const nPassed = results.filter(x => x).length;
if (nPassed === results.length) {
	document.body.textContent = `💫 All ${results.length} tests passed! 💫`;
	console.log(`💫 All ${results.length} tests passed! 💫`);
} else {
	document.body.textContent = `${nPassed - results.length} of ${results.length} tests failed.`;
	console.log(
		`${nPassed} of ${results.length} tests passed:`,
		results.map((r, i) => `${i}: ${r ? 'PASS' : 'FAIL'}`)
	);
	results.forEach((result, i) => {
		if (!result) {
			console.log(`\n--- Test case ${i + 1}: expected vs. actual result ---`);
			const [str, expectedResult] = testCases[i];
			console.log(expectedResult, parse(str));
		}
	});
}

## test.html
<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<meta http-equiv="X-UA-Compatible" content="IE=edge">
	<meta name="viewport" content="width=device-width, initial-scale=1.0">
	<title>Brackets tester</title>
	<style>
		html {
			font: 30px -apple-system, BlinkMacSystemFont, avenir next, avenir, helvetica neue, helvetica, Ubuntu, roboto, noto, segoe ui, arial, sans-serif;
			place-content: center;
			display: grid;
			height: 100vh;
		}
	</style>
</head>
	<body>
		<script src="./brackets.js"></script>
	</body>
</html>
	/**
	* Parse takes a string and returns a nested array. The array nests
	* to a deeper level for each [[enclosed double bracket pair]].
	*
	* eg:
	*
	* // Output: ['It goes ', ['deeper and ', ['deeper.']]]
	* parse('It goes [[deeper and [[deeper.]]]]');
	*/
	function parse(str, startIdx = 0, isChild = false) {
	const result = [];
	for (let i = startIdx + 1, _len = str.length; i < _len; ++i) {
	const char = str[i];
	let isOpen = false,
	isClosed = false;
	if (char === str[i - 1]) {
	if (char === '[') isOpen = true;
	else if (char === ']') isClosed = true;
	}
	if (isOpen \|\| isClosed) {
	// Ensure the possible substring between the prior token and here is captured.
	if (i > startIdx + 1) result.push(str.slice(startIdx, i - 1));
	if (isOpen) {
	const [contents, nextIdx] = parse(str, i + 1, true);
	result.push(contents);
	i = startIdx = nextIdx;
	} else if (isClosed) {
	return isChild ? [result, i + 1] : result;
	}
	}
	}
	if (str.length !== startIdx) result.push(str.slice(startIdx, str.length));
	return isChild ? [result, str.length] : result;
	}

	// Tests below here.
	const testCases = [
	['A simple string', ['A simple string']],
	['A simple string [ [ [][][] ] ] with single brackets', ['A simple string [ [ [][][] ] ] with single brackets']],
	['[[An enclosed string]]', [['An enclosed string']]],
	['[[Each]][[word]][[separately]][[enclosed]]', [['Each'], ['word'], ['separately'], ['enclosed']]],
	['[[Some words are enclosed]] but some are not', [['Some words are enclosed'], ' but some are not']],
	[
	'This [[[[is a test]] of some nested groups]] and the [[resulting]] data structure [[should [[be [[nested]] accordingly]]]]',
	[
	'This ',
	[['is a test'], ' of some nested groups'],
	' and the ',
	['resulting'],
	' data structure ',
	['should ', ['be ', ['nested'], ' accordingly']],
	],
	],
	['This: ]] will close early…', ['This: ']],
	['This: [[[[[[ will close at the end…', ['This: ', [[[' will close at the end…']]]]],
	['This will have an empty array at the end: [[', ['This will have an empty array at the end: ', []]],
	['', []],
	];
	// Util.
	function miniDeepArrayCompare(array1, array2) {
	return (
	Array.isArray(array2) &&
	array1.length === array2.length &&
	array1.every((a, i) => {
	const b = array2[i];
	return Array.isArray(a) ? miniDeepArrayCompare(a, b) : a === b;
	})
	);
	}
	const results = testCases.map(([str, expectedResult]) => miniDeepArrayCompare(parse(str), expectedResult));
	const nPassed = results.filter(x => x).length;
	if (nPassed === results.length) {
	document.body.textContent = `💫 All ${results.length} tests passed! 💫`;
	console.log(`💫 All ${results.length} tests passed! 💫`);
	} else {
	document.body.textContent = `${nPassed - results.length} of ${results.length} tests failed.`;
	console.log(
	`${nPassed} of ${results.length} tests passed:`,
	results.map((r, i) => `${i}: ${r ? 'PASS' : 'FAIL'}`)
	);
	results.forEach((result, i) => {
	if (!result) {
	console.log(`\n--- Test case ${i + 1}: expected vs. actual result ---`);
	const [str, expectedResult] = testCases[i];
	console.log(expectedResult, parse(str));
	}
	});
	}
	<!DOCTYPE html>
	<html lang="en">
	<head>
	<meta charset="UTF-8">
	<meta http-equiv="X-UA-Compatible" content="IE=edge">
	<meta name="viewport" content="width=device-width, initial-scale=1.0">
	<title>Brackets tester</title>
	<style>
	html {
	font: 30px -apple-system, BlinkMacSystemFont, avenir next, avenir, helvetica neue, helvetica, Ubuntu, roboto, noto, segoe ui, arial, sans-serif;
	place-content: center;
	display: grid;
	height: 100vh;
	}
	</style>
	</head>
	<body>
	<script src="./brackets.js"></script>
	</body>
	</html>