Zigzag Conversion

LeetCode題目: 6. Zigzag Conversion

My solution:

/**
 * @param {string} s
 * @param {number} numRows
 * @return {string}
 */
let convert = (s, numRows) => {
    let stack = [], count = 0, ASSwitch = true;
    for(const char of s) {
        stack[count] ? stack[count].push(char) : stack[count] = [char];
        if(ASSwitch) {
            ++count;
            if(count === numRows - 1) ASSwitch = false;
        }
        else {
            --count;
            if(count === 0) ASSwitch = true;
        }
    }
    return stack.flat().join('');
};