最长公共前缀

function longestCommonPrefix(strs) {
    let str = ‘‘
    if(strs.length == 0){
        return str
    }
    let baseStr = strs[0]
    for(let i = 0;i < baseStr.length;i++){
        let item = baseStr[i]
        for(let j = 1;j < strs.length;j++){
            let jItem = strs[j]
            if(item != jItem[i]){
                return str
            }
        }
        str += item
    }
    return str
}