Why does `filter` trigger some many times? [duplicate]

Question

http://plnkr.co/edit/b1yGAwkzojF4BFWgpMsv?p=preview

Why did filter trigger some many times?

I guess {{name|test}} will tigger twice because the name is null at first, then got value at controller.

Why did it trigger filter when include template?

Answer 1

Every filter is called at least once every digest cycle. This SO answer has a fiddle that demonstrates this.

When a template is loaded, you are in a digest cycle, so all filters will be called.