Discussion on: What is the difference between Methods, Computed, and Watchers?

When to use methods

• To react on some event happening in the DOM
• To call a function when something happens in your component. You can call a methods from computed properties or watchers.

When to use computed properties

• You need to compose new data from existing data sources
• You have a variable you use in your template that’s built from one or more data properties
• You want to reduce a complicated, nested property name to a more readable and easy to use one, yet update it when the original property changes
• You need to reference a value from the template. In this case, creating a computed property is the best thing because it’s cached.
• You need to listen to changes of more than one data property

When to use watchers

• You want to listen when a data property changes, and perform some action
• You want to listen to a prop value change
• You only need to listen to one specific property (you can’t watch multiple properties at the same time)
• You want to watch a data property until it reaches some specific value and then do something

(source :) )