javascript - 未捕获的 TypeError : postData(. ..).then 不是一个函数

Question

我设置了一个按钮，单击该按钮时将通过获取发布数据并创建一个警报。但是，我首先检查以确保某些输入不为空。如果输入元素没有值，我会尝试返回一个字符串，告诉我哪个输入元素值为空。当我这样做时，会出现“Uncaught TypeError: postData(...).then is not a function”错误。我也看过Uncaught TypeError: $.get(...).then is not a function但无法弄清楚。任何帮助将不胜感激。谢谢你!

document.getElementById("sbmForm").onclick = function () {postData(`/projectInfo`)
    .then(result => alert(JSON.stringify(result))) // JSON-string from `response.json()` call
    .catch(error => alert(error))};



function postData(url = ``) {
    // get form data from local storage
    var data = {};
    var unqVal = document.getElementById("unq_num").innerHTML;
    unqVal = "--??**" + unqVal;

    // keys that can not be empty
    var notEmpty = ["comp_name", "compaddr_str_num", "compaddr_str_nam", "compaddr_city",
        "compaddr_state", "compaddr_zipcode", "proj_name", "projaddr_str_num", "projaddr_str_nam",
        "projaddr_city", "projaddr_state", "projaddr_zipcode", "contact_fname", "contact_date"];
    /* get all keys and values from local storage and store them in dict to send to server */
    var keys = Object.keys(localStorage);

    var i;
    for (i=0; i < keys.length; i++){

        var val = localStorage.getItem(keys[i]);

        // if unq val is in string, add it to the data
        var indexOf = keys[i].indexOf(unqVal);

        if (indexOf != -1){

            var keyNU = keys[i].substring(0, indexOf);
            // if value is in array
            if (notEmpty.includes(keyNU)){
                // if value is empty
                if (!val){
                    alert(keyNU + " cannot be empty!");

                    /**** ERROR OCCURS HERE *****/
                    return keyNU + " cannot be empty!";
                }
            }

            data[keys[i]] = val;
        }

    }

    // Default options are marked with *
    return fetch(url, {
        method: "POST",
        headers: {
            "Content-Type": "application/json",
        },
        body: JSON.stringify(data), // body data type must match "Content-Type" header
    })
    .then(response => response.json()); // parses response to JSON
};

Answer 1

您返回的是字符串值，而不是 promise当检测到“错误”时。 then 方法只存在于 promises 上。

将您的函数更改为async所以它默认返回一个 promise。

async function postData(url = ``){}

---

然后在需要发生的时候抛出一个错误(会被catch方法捕获)通过改变这个

/**** ERROR OCCURS HERE *****/
return keyNU + " cannot be empty!";

到

throw new Error(keyNU + " cannot be empty!");

---

最后，对于您的提取:

//fetch returns a promise, so use await
const res = await fetch(url, {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
    },
    body: JSON.stringify(data), // body data type must match "Content-Type" header
});

//res.json() returns a promise, so use await
return await res.json();