Brackets

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 ")".

Hints
• push left brackets into an array L1
• compare non-left brackets with L1.pop()

function isPair(c1, c2){
    if( c1=='(' && c2==')' ) return true
    if( c1=='{' && c2=='}' ) return true
    if( c1=='[' && c2==']' ) return true
    return false
}

function solution(S) {
    // write your code in JavaScript (Node.js 8.9.4)
    if(S.length < 1) return 1
    
    let L = ['(', '{', '[']
    let L1 = []
    let c 
    
    for(let i=0; i<S.length; i++){
        if( L.includes(S[i])){ // Left brackets
            L1.push(S[i])
        } else { // Right brackets
            if(L1.length < 1) return 0 // no left barckets for matching
            c = L1.pop()
            if( !isPair(c, S[i])) return 0
        }
    }
    if( L1.length < 1) return 1 // all popped out
    else return 0 // Let brackets remaining
}