Understand the Primary Function of 'Computed' Properties in Vue.js

In Vue.js, 'computed' properties play a crucial role. The main function of computed properties is to calculate derived state based on reactive data.

When you're dealing with complex logic, computed properties simplify code by executing operations for you. These operations might include string manipulation, computation of values, and more, which depend on the application's data.

Here's an example: let's say you have a Vue.js application where a user can enter their first and last name. You need to display the full name as well, deriving it from the given names. This is where a computed property becomes useful. Have a look at the following code snippet:

new Vue({
  el: '#app',
  data: {
    firstName: '',
    lastName: ''
  },
  computed: {
    fullName: function() {
      return this.firstName + ' ' + this.lastName;
    }
  }
})

In this example, 'fullName' is a computed property that depends on 'firstName' and 'lastName'. Whenever any of the dependent properties change, Vue.js automatically updates 'fullName'. Besides keeping your code cleaner, these properties also cache their results. This caching is efficient and saves computational resources, especially when handling large datasets or expensive operations.

As a best practice, use computed properties when you need to change data before displaying it. This idea is called data transformation, which is an integral part of creating meaningful, user-friendly interfaces.

Computed properties have the power to handle logic, perform calculations, and update themselves. They essentially offload some of the burdens from your templates, making your Vue.js code cleaner, faster, and more intuitive. For more complex applications, computed setters can also be used to perform reverse operations, thereby increasing the versatility and usefulness of computed properties.