Understanding the Vue.set Method in Vue.js

Vue.js is a powerful JavaScript framework used for building modern web applications. One important feature of Vue.js is its ability to update the DOM efficiently by reactivity. But sometimes, we may want to trigger reactivity manually. Here comes into play the Vue.set method.

Vue.set is a crucial function in Vue.js, which aids in manually triggering reactivity, especially for objects and arrays that may not be made reactive by default. Let's dive deep into this concept.

Vue.set in Action

Vue.set(object, key, value)

In the code snippet above, Vue.set takes three arguments. The object refers to the target object we want to change, key is the property we want to modify, and value is the new value we want to set.

Below is an example of the Vue.set method:

let vm = new Vue({
  data: {
    tasks: {
      task1: 'Finish the project',
      task2: 'Check emails'
    }
  }
})
 
Vue.set(vm.tasks, 'task3', 'Attend meeting')

In this example, we added a third task to our tasks data object using Vue.set. This action is reactive, and Vue.js will immediately update any bindings or computations dependent on tasks.

When to Use Vue.set

Normally, Vue.js tracks any changes automatically, but sometimes we need to add a property to an object after it's been created and Vue.js is unable to track such changes. This situation happens mostly when adding new properties to an object or indexing an array with a non-existent index. Vue.set comes in very handy in these situations where the automatic reactivity system of Vue.js falls short.

Best Practices

While Vue.set is very useful, it should not be abused. Using it unnecessarily can lead to performance issues because it forces Vue.js to immediately rerun the dependencies. Using Vue's built-in methods (like push for arrays) is preferred where possible as Vue modifies these to be reactive.

In conclusion, Vue.set is a beneficial tool that can be used for enhancing Vue.js's reactivity system. It is particularly useful when we need to add reactive properties to an object after it's been created. However, it's a tool to be used sparingly, as unnecessary use can lead to performance issues.