Node.js从数组文本提取订单日期与总额报错求助

问题场景 #

现有订单JSON数据及读取代码：

let rawdata = fs.readFileSync('test.json');
let orders = JSON.parse(rawdata);

原始JSON数据：

[{"order":["Awaiting delivery","Order date: Dec 18, 2022","Order ID: 11111111","Copy","Order details","store name","product name","1, 1","US $1.73x1","Total: US $5.39","Confirm receipt","Track order"]},{"order":["Awaiting delivery","Order date: Dec 18, 2022","Order ID: 2222222","Copy","Order details","store name_2","5","items","Total: US $13.07","Confirm receipt","Track order"]}]

编写提取订单日期、ID、店铺名和总额的代码后，报错TypeError: Cannot read properties of undefined (reading 'includes')，且无法正确获取订单总额：

orders.forEach(element => {
let order_date = element.order[1].replace('Order date:', '')
let order_ID = element.order[2].replace('Order ID:', '')
let store_name = element.order[5]
for (i=0; i<15; i++) {
    if (element.order[i].includes('Total')) {
        let order_total = element.order[i]
    }
}
console.log(order_date + "*" + order_ID + "*" + store_name + "*" + order_total)
});

预期输出：

Dec 18, 2022*11111111*store name*Total: US $5.39
Dec 18, 2022*2222222*store name_2*Total: US $13.07

问题原因 #

1. 数组越界访问：循环条件设为i<15，但实际每个order数组的长度仅为11或12，当i超过数组最大索引时，element.order[i]返回undefined，调用includes()方法就会触发报错。
2. 变量作用域错误：order_total在for循环的if块内用let声明，属于块级作用域，外部的console.log无法访问该变量，会输出undefined。
3. 方法使用错误：JavaScript字符串没有contains()方法，正确的包含判断方法是includes()。

修复方案 #

方案1：修正循环逻辑与作用域 #

orders.forEach(element => {
    let order_date = element.order[1].replace('Order date:', '').trim(); // 去除多余空格
    let order_ID = element.order[2].replace('Order ID:', '').trim();
    let store_name = element.order[5];
    let order_total = ''; // 提前声明变量，扩大作用域
    // 循环到数组实际长度，避免越界
    for (let i = 0; i < element.order.length; i++) {
        if (element.order[i].includes('Total')) {
            order_total = element.order[i];
            break; // 找到目标后直接跳出循环，提升效率
        }
    }
    console.log(`${order_date}*${order_ID}*${store_name}*${order_total}`);
});

方案2：使用数组find方法简化代码 #

利用数组的find()方法直接匹配包含"Total"的元素，代码更简洁：

orders.forEach(element => {
    let order_date = element.order[1].replace('Order date:', '').trim();
    let order_ID = element.order[2].replace('Order ID:', '').trim();
    let store_name = element.order[5];
    let order_total = element.order.find(item => item.includes('Total'));
    console.log(`${order_date}*${order_ID}*${store_name}*${order_total}`);
});

内容的提问来源于stack exchange，提问作者Lord