Shortcut to checking if a value exist in an object

So I’m trying to get a shortcut to return a value in an object. For example,

const days = {
 Monday: 4,
 Thursday: 3,
 Friday: 1
} 

Now, if I want to do days.Thursday, that value will be undefined, so if I do days.Thursday, it will return undefined, but I would like for it to return 0, if it is undefined. My method of doing this would be to do:

days.Thursday?days.Thursday:0

But doing this is very repetitive and I’d have to do it at least 7 times, for each day of the week, considering this object is being set based off of data from firebase.

Answer

You can use ?? (the nullish coalescing operator) to default to a different value if the expression on the left is undefined (or null):

const thursdayVal = days.Thursday ?? 0;

I’d have to do it at least 7 times, for each day of the week

Consider iterating over an array of property names instead, eg

const dayNames = ['Monday', 'Tuesday', 'Wednesday', /* ... */];
for (const dayName of dayNames) {
  // do something with days[dayName] ?? 0
}