Interview test: Bracket matching

With test suite

by Jason Green

HTML

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  <strong>User Logs</strong>
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CSS

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#HTMLReporter .symbolSummary li { display: block; float: left; height: 7px; width: 14px; margin-bottom: 7px; font-size: 16px; }
#HTMLReporter .symbolSummary li.passed { font-size: 14px; }
#HTMLReporter .symbolSummary li.passed:before { color: #5e7d00; content: "\02022"; }
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#HTMLReporter .runningAlert { background-color: #666666; }
#HTMLReporter .skippedAlert...

JavaScript

const OPENS = "{[(";
const CLOSES = "}])"

const MATCHES = {
	"{": "}",
  "[": "]",
  "(": ")"
}


function isBalanced(str) {
	let stack = [];
  
  for (let char of str) {
  	if (OPENS.includes(char)) {
    	stack.push(char);
    } else if (CLOSES.includes(char)) {
    	const openingChar = stack.pop();
      if (MATCHES[openingChar] !== char) {
      	return false;
      }
    }
  }
  return stack.length === 0;
}





describe("isBalanced", function() {
  it("should return true for strings with balanced parenthesis", function() {
    expect(isBalanced('(())')).toBe(true, '(())');
    expect(isBalanced('()()')).toBe(true, '()()');
    expect(isBalanced('(()')).toBe(false, '(()');
    expect(isBalanced(')(')).toBe(false, ')(');
    expect(isBalanced('(()))(')).toBe(false, '(()))(');
  });
  
  it("should support other types of brackets too", function() {
    expect(isBalanced('{[()]}')).toBe(true, '{[()]}');
    expect(isBalanced('{}()')).toBe(true, '{}()');
    expect(isBalanced('{}()}')).toBe(false, '{}()}');
    expect(isBalanced('{[}]')).toBe(false, '{[}]');
    expect(isBalanced('{[{}}]')).toBe(false, '{[{}}]');
  });
});









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