SOURCE

function findTree(codeArr, treeArr){
    var titles = [];
    function findTitle(arr, code){
        arr.some(item => {
            if(item.code === code){
                titles.push(item.title);
                return true
            }else if(item.children){
                findTitle(item.children, code);
            }
        });
    }

    codeArr.forEach(code => {
        findTitle(treeArr, code);
    });

    console.log(titles.join());
    return titles;
}

var codeArr = [
    'code1',
    'code2',
    'code3',
];

var treeArr = [
    {
        id: 1,
        code: 'code1',
        title: '编码1',
        children: [
            {
                id: 2,
                code: 'code3',
                title: '编码3',
                pid: 1
            },
        ]
    },
    {
        id: 3,
        code: 'code4',
        title: '编码4',
        children: [
            {
                id: 4,
                code: 'code4',
                title: '编码4',
                pid: 3,
                children: [
                    {
                        id: 5,
                        code: 'code2',
                        title: '编码2',
                        pid: 4
                    },
                ]
            },
        ]
    }
];

findTree(codeArr, treeArr);