[Question] Why is iterating over range.areas.getItemAt(x) so much faster than calling range.areas.load('items')? about office-js

[XuanZhouMSFT]

@hdwatts Thanks for the waiting. I did a quick investigation and found it should caused by the "areas.load('items')" you are using in the first code. With this line, we will try to load all properties for Range/RangeAreas. It will cost a lot of time/resource to do that.
For example, with the below code we can see the result is:

areas.load("items");
console.log("before: " + JSON.stringify(areas));
await context.sync();
console.log("after: " + JSON.stringify(areas));

So we'd like to suggest you to only load the properties you need.

[hdwatts]

@XuanZhouMSFT

In my first code example, I'm doing what you do (loading all the items). I agree, this is loading a lot of data.

However, in my second code example, I'm loading what I believe to be the same data (loading all the items). I'm just iterating over the number of items and using the getItemAt() method.

The latter example runs in drastically less time, but accomplishes the same thing. Is there a difference between these two methods?

[XuanZhouMSFT]

@hdwatts They are different. The RangeArea.getItemAt() method will only return an object for rangeCollection. Within this object, the properties are not loaded. If you want to use the property inside it, you will also need to load it/them, wait for the the context.sync and then get. And if you directly get the property, it will throw exception.

[hdwatts]

Aha! Thank you so much @XuanZhouMSFT! That answers it for me and satisfies my curiosity :). Thanks again!