Promise提前resolve返回缺失Ajax数据，如何等待异步请求完成后返回完整数组

• Promise的resolve方法一旦调用就会终结当前Promise的状态，你原有代码里每处理完1个带variant参数的URL，或者1个Ajax请求成功后，就直接调用resolve(obj)，导致第一个任务完成就提前返回，根本不会等待其他异步请求结束。
• 循环里的异步任务没有做统一的等待管理，无法感知所有任务的完成时机。
• 原有Ajax的error回调、参数校验逻辑中直接throw的错误无法被外层Promise的catch捕获，会直接抛出为全局异常。

核心思路是把每个URL的处理逻辑都封装为独立Promise，同步的直接resolve结果，异步的Ajax请求在success回调里resolve结果，最后用Promise.all等待所有任务完成后统一返回结果数组，天然保证结果顺序和输入URL顺序一致。

function getProducts(product_links, product_quantity, trigger_word){
    // 提前做全局参数合法性校验，不合法直接返回reject状态的Promise
    if(trigger_word == ''){
        return Promise.reject(new Error("Something went wrong, please check trigger word enterd field!"));
    }
    if(!(product_links.length > 0 && product_quantity.length > 0 && product_links.length == product_quantity.length)){
        return Promise.reject(new Error("Something went wrong, please check all product link fields and their quantity!"));
    }
    // 存储每个URL对应的处理Promise
    const taskList = [];
    for (let i = 0; i < product_links.length; i++){
        const linkVal = $(product_links[i]).val();
        const quantityVal = $(product_quantity[i]).val();
        // 单条数据校验不合法直接reject整个任务
        if(linkVal == '' || quantityVal == '' || !isUrl(linkVal) || !$.isNumeric(quantityVal) || quantityVal <= 0){
            return Promise.reject(new Error("Something went wrong, please check all product link fields and their quantity!"));
        }
        const url = new URL(linkVal);
        const search_params = url.searchParams;
        // 每个处理逻辑包装成Promise推入任务列表
        if(search_params.has("variant")){
            // 带variant参数的同步逻辑，直接resolve结果
            const res = {
                id: parseInt(search_params.get("variant")),
                quantity: parseInt(quantityVal)
            };
            taskList.push(Promise.resolve(res));
            console.log("Product with variant: ", res);
        }else{
            // 无参数的异步Ajax逻辑，封装成Promise推入
            taskList.push(new Promise((resolve, reject) => {
                const product_json = `${linkVal}.json`;
                $.ajax({
                    crossDomain: true,
                    type: "GET",
                    contentType: "application/json; charset=utf-8",
                    url: product_json,
                    dataType: "jsonp",
                    headers:{
                        "Access-Control-Allow-Origin": "*"
                    },
                    success: function(res){
                        const first_variant_id = res['product']['variants'][0]['id'];
                        const product_name = res['product']['title'];
                        const quantity_value =  parseInt(quantityVal);
                        const result = {
                            id: first_variant_id,
                            quantity: quantity_value
                        };
                        console.log("Product name: ", product_name , "Product id: ", first_variant_id, "Quantity: ", quantity_value);
                        resolve(result);
                    },
                    error:function(err) {
                        reject(new Error("Something went wrong, please check your internet connection and try again later!"));
                    }
                });
            }));
        }
    }
    // 等待所有任务完成后返回所有结果组成的数组
    return Promise.all(taskList);
}

// 原有调用逻辑无需改动
getProducts(product_links, product_quantity, trigger_word)
.then(function (products) {
    console.log(products);
    console.log(products.length);
    products.forEach(function(variant){
        console.log(variant);
    });
})
.catch(function (err){
    console.log(err);
});

内容的提问来源于stack exchange，提问作者Stefan Momcilovic