Codility - Brackets (JavaScript)

Task Description:
A string S consisting of N characters is considered to be properly nested if any of the following conditions is true:
S is empty;
S has the form "(U)" or "[U]" or "{U}" where U is a properly nested string;
S has the form "VW" where V and W are properly nested strings.
For example, the string "{[()()]}" is properly nested but "([)()]" is not.

Write a function:
function solution(S);
that, given a string S consisting of N characters, returns 1 if S is properly nested and 0 otherwise.
For example, given S = "{[()()]}", the function should return 1 and given S = "([)()]", the function should return 0, as explained above.
Write an efficient algorithm for the following assumptions:
N is an integer within the range [0..200,000];
string S consists only of the following characters: "(", "{", "[", "]", "}" and/or ")".

[fredteixeira]

I basically did almost the same thing, but didn't check if it isBracket, and got only 75%. This is quite confusing, the last part of the description mention that only brackets should be included in S.

function solution(S) {

if (S.length === 0) {
return 1;
}

var map = new Map();
map.set(']', '[');
map.set('}', '{');
map.set(')', '(');

// console.log(S);
var stack = [];
var arr = S.split('');
stack[0] = arr[0];
for (var i=1; i<arr.length; i++) {
var pair = map.get(arr[i]);
if(pair === stack[stack.length-1]){
stack.pop();
} else {
stack.push(S[i]);
}
}
return stack.length === 0 ? 1 : 0;
}