最长公共前缀

/**
 * @param {string[]} strs
 * @return {string}
 */
var longestCommonPrefix = function (strs) {
    if (!strs.length) return '';
    const [a, ...b] = strs;
    let res = "";
    for (let i = 0; i < a.length; i++) {
        let flag = b.every(item => item[i] == a[i])
        if (flag) {
            res = res + a[i]
        } else {
            break
        }
    }
    return res
};