const testArr = [{
    "k1": {
        "k3ad": "df",
        "k0": {
            "user": "xia0ming",
            "age": "18"
        },
    },
    "ke.name": "danshi"
}, {
    "k1": {
        "k3ad": "dfsdf",
        "k0": {
            "user": "xia0ming",
            "age": "28"
        },
    },
    "ke.name": "dadfnshi"
}];

const res = [{
    "k1.k3ad": "df",
    "ke.name": "danshi"
}, {
    "k1.k3ad": "dfsdf",
    "ke.name": "dadfnshi"
}]

function getTbodyData(originArr, filter) {
    const rawArr = originArr.slice();
    const getFirstExist = function(data, item) {
        if (data[item]) {
            return data[item];
        } else {
            let index = item.indexOf('.');
            return index !== -1 ? getFirstExist(data[item.substring(0, index)], item.substring(index+1)) : undefined;
        }
    };

    return rawArr.reduce( (newArr, data) => {
        newArr.push(filter.reduce( (prev, item) => {
            prev[item] = getFirstExist(data, item);
            return prev;
        }, {}));
        return newArr;
    }, []);
}

function deepEqual(a, b) {
    return JSON.stringify(a) === JSON.stringify(b);
}

console.log(deepEqual(getTbodyData(testArr, ["k1.k3ad","ke.name"]), res));

你能取到k3.ad完全是因为这个属性名就叫k3.ad啊，data[k1.k3ad] 并不等于 data.k1.k3ad，所以你这么写是无效的。

准确的说，你这个例子里，点运算符.和属性名内部的点并不能区分，k1.k3ad中是作为点运算符取属性，k3.ad中则是属性名自带的点，你告诉我这要函数怎么区分？

要实现这个功能的话首先还是修改你的json格式吧，或者把k1.k3ad这种需求情况下的参数改为[k1][k3ad]之类的格式。

var getTbodyData = testArr.map(item => { 
    return { 'k1.k3ad': (item.k1 && item.k1.k3ad) || '无', 'ke.name': item['ke.name'] };
});

根据你的方法进行的修改

var  getTbodyData= function (ajaxdata, filterArr) {
            var arr = [];
            ajaxdata.forEach(function (data, i) {
                arr.push({});
                filterArr.forEach(function (key) {
                    var k_arr = key.split('.'),k,a = arr[i],j = 0;
                    var d = data;

                    if(d[key]){
                        a[key] = d[key];
                    }else{
                        while(k = k_arr[j++]){
                            d = d[k];
                        }
                        a[key] = d;
                    }
                    
                    
                });
            });
            return arr;
        };