I have a defined interface here:
interface Notification {
fullDate: string;
weekday: string;
info: {
title: string;
subtitle: string;
read: boolean;
};
}
Later, I have defined a const that is of that type:
const orderedNotifications: { [month: string]: Notification[] } = {};
I get the data from outside and use a foreach loop where I get a list of objects with data retrieved from the same months. I want to check if the object has that month as a key and if not, create it and push all the data of similar months to that key. I tried like this:
orderedNotifications[month].push({
fullDate,
weekday,
info,
});
Where month is the variable with the month of the post. Unfortunately, I get a TypeError: Cannot read properties of undefined (reading 'push')
You are getting TypeError: Cannot read properties of undefined (reading 'push') because month key is not defined within orderedNotifications object.
Use the following code:
// This line will solve your issue as it is
// checking if the key already exist do nothing
// otherwise set empty array on it.
orderedNotifications[month] = orderedNotifications[month] || [];
orderedNotifications[month].push({
fullDate,
weekday,
info,
});
Just add an if check and add it if it isn't there already... silly me.
if (!(month in orderedNotifications)) {
orderedNotifications[month] = [
{
fullDate,
weekday,
info,
},
];
} else {
orderedNotifications[month].push({
fullDate,
weekday,
info,
});
}