showEvaluationList移动到上边后为什么evaluationList变成undefined？

showEvaluationList: function (bookId, isFlush) {
    axios.get("/api/evaluation/list?bookId=" + bookId)
        .then(function (response) {
            const json = response.data
            if (json.code == "0") {
                if(isFlush){
                    this.evaluationList.splice(0, this.evaluationList.length)
                }
                const list = json.data.list;
                list.forEach(function (item) {
                    item.ct = formatDate(item.create_time);
                    this.evaluationList.push(item)
                })
            } else {
                console.error(json)
            }
        })

这里的objApp我直接都替换成this了

报错截图：