如何从字符串中删除成对的相同数字？

function removeMatchingPairs(str) {
    let stack = [];

    for (let i = 0; i < str.length; i++) {
        let char = str[i];

        if (stack.length > 0 && stack[stack.length - 1] === char) {
            stack.pop();
        } else {
            stack.push(char);
        }
    }

    return stack.join('');
}

let input = "112233445566";
let result = removeMatchingPairs(input);
console.log(result);  // 输出 "123456"