Beeswax code challenge

beeswax.js

// Timed response to problem:
// https://drive.google.com/file/d/0B4I3zDNqwzpCZ1BmbTN6TEJxTGVYZWV5WEtTR3BmZ08zdlF3/view
// time taken: 8 minutes.

let strings = [
    'hello world',
    '{} ',
    '{{{foo();}}}{} ',
    '{{}{}} ',
    '{{{}',
    '} ',
    '{}{foo{}',
];


function customStack(){
    let ourStack = []
    return {
        push: function(item){
            ourStack.push(item)
        },
        pop: function(){
            return ourStack.length > 0 ? ourStack.splice(ourStack.length-1) : -1
        },
        peek: function(){
            return ourStack.length > 0 ? ourStack[ourStack.length-1] : -1
        },
        toArray: function(){
            return ourStack
        },
        length: function(){
            return ourStack.length
        }
    }
}

for( x in strings ){
    let string = strings[x]
    let ourStack = customStack()
    let balanced = true
    for( let y in string ){
        let char = string[y]
        if( char === '{' ) {
            ourStack.push(y)
        }  else if( char === '}' ){
            let z = ourStack.pop()
            // unmatched
            if( z === -1 ){
                balanced = false
                console.log(
                    'string: %s unmatched ending bracket at %s',
                    string,
                    y
                )
            }
        }
    }
    if(ourStack.length() > 0){
        console.log(
            'string: %s unmatched starting bracket at location(s): %s',
            string,
            ourStack.toArray().join(',')
        )
    } else if( balanced ){
        console.log('string: %s balanced', string);
    }

}