Implement function check (text) which checks whether brackets within text are correctly nested. You need to consider brackets of three kinds: (), [], {}.

bracketsMatchingTest.js

var expect = require('expect')
var _matches = {
    '{': { invert: '}', isOpening: true },
    '}': { invert: '{', isOpening: false },
    '(': { invert: ')', isOpening: true },
    ')': { invert: '(', isOpening: false },
    '[': { invert: ']', isOpening: true },
    ']': { invert: '[', isOpening: false }
};

function check (input) {
    var bracketsStack = [];
    for (var index = 0; index < input.length; index++) {
        var char = input[index];
        if(!_matches[char]) continue; // not a bracket
        
        if (!_matches[char].isOpening) {
            if(bracketsStack.length == 0 || bracketsStack[bracketsStack.length - 1] != _matches[char].invert)
                return false; // no opening bracket for a currently closing found
            else
                bracketsStack.pop();            
        }
        else if (_matches[char].isOpening)
            bracketsStack.push(char);
    }
    return bracketsStack.length == 0;
}

expect(check("a(b)")).toBe(true);
expect(check("[{}]")).toBe(true);
expect(check("[(]")).toBe(false);
expect(check("[(])")).toBe(false);
expect(check("[}")).toBe(false);
expect(check("}{")).toBe(false);
expect(check("z([{}-()]{a})")).toBe(true);
expect(check("")).toBe(true);