Attached is a node.js route for displaying product data for the product ids that a user enters in an html form. In this route, I have the array ‘prod_id_arr’ with product ids. For each prod_id in this array, I select the mysql product database row and add it to another array ‘data’. I then use the ‘data’ array to display the product data in “prod_multi_upd_pg” view at the end. When I console.log the data array, I see it is populated. However, it fails in the “prod_multi_upd_pg” view with the message “Cannot read properties of undefined (reading ‘prod_id’)”. Interesting thing is that when I assign a single occurrence of the data array (i.e. data[0] or data[1]) to another array adata and pass the adata array to the ejs view, it works for that single item. I don’t understand how js logic works, it is very confusing. What do I have to do to display all items? Any help will be appreciated.
// Route to display current data for multiple product updates.
app.get('/prod_multi_upd_pg', async (req, res) => {
let prod_id_arr = req.query.prod_id_arr.split(',');
let data = [];
const fetchData = async (prod_id, index) => {
return new Promise((resolve, reject) => {
con.query('SELECT * FROM product WHERE prod_id = ?', [prod_id], function(err, row) {
if (err) {
reject(err);
} else {
resolve(row.length === 0 ? null : row);
console.log("row: ", row)
}
});
});
};
try {
const dataPromises = prod_id_arr.map((prod_id, index) => fetchData(prod_id));
const data = await Promise.all(dataPromises);
res.render("prod_multi_upd_pg", {data}); --> this doesn't work.
But when I replace this line with the following 3
lines, it works for that single item.
let adata = [];
adata = data[0];
res.render("prod_multi_upd_pg", { adata });
} catch (error) {
alert("Ürün kodu bulunamadı, lütfen geçerli bir ürün kodu girin.");
res.status(500).send("Internal Server Error");
}
})<tbody>
<% if(data.length){for(let i = 0; i< data.length; i++) {%>
<tr>
<td><%=data[i].prod_id%></td>
<td><%=data[i].saleprice%></td>
<td><%=data[i].stock_quantity%></td>
<td><%=data[i].max_order_qty%></td>
<td><%=data[i].time_to_cargo%></td>
</tr>
<%} }else{ %>