Category: Vue

To test if an input is focused using Vue Test Utils, you can use the wrapper.find() method to select the input element and then check its element property to see if it’s focused.

To do this we can write something like

import { mount } from '@vue/test-utils';
import YourComponent from '@/components/YourComponent.vue'; // import your component

describe('YourComponent', () => {
  it('should focus on input when clicked', async () => {
    const wrapper = mount(YourComponent); // mount your component

    // Find the input element
    const input = wrapper.find('input');

    // Simulate a focus event on the input
    await input.trigger('focus');

    // Check if the input is focused
    expect(input.element === document.activeElement).toBe(true);
  });
});

In this example, mount(YourComponent) mounts your Vue component for testing.

wrapper.find('input') selects the input element within the component.

await input.trigger('focus') simulates a focus event on the input element.

input.element === document.activeElement checks if the input element is currently focused.

To blur an element when it’s clicked in Vue.js, you can use a combination of Vue directives and data binding.

For example we write

<template>
  <div>
    <button @click="blurElement">Click to blur</button>
    <div :class="{ blurred: isBlurred }">
      <!-- Your content here -->
      <p>This is a blurred element</p>
    </div>
  </div>
</template>

<script>
export default {
  data() {
    return {
      isBlurred: false
    };
  },
  methods: {
    blurElement() {
      // Toggle the isBlurred flag when the button is clicked
      this.isBlurred = !this.isBlurred;
    }
  }
};
</script>

<style>
.blurred {
  filter: blur(5px); /* Apply the blur effect */
}
</style>

In this example, wWe have a button that, when clicked, triggers the blurElement method.

The blurElement method toggles the value of isBlurred between true and false.

We use a conditional class binding (:class="{ blurred: isBlurred }") to apply the blurred class to the element when isBlurred is true.

The .blurred class in the style section applies the blur effect using CSS filter: blur(5px);.

Now, when you click the button, the element will toggle between being blurred and not being blurred.

Adjust the blur effect by changing the value in the filter: blur() CSS property.

Waiting for data before rendering in Vue.js typically involves utilizing conditional rendering or loading states.

To do this we write:

<template>
  <div v-if="dataLoaded">
    <!-- Your content here -->
    {{ data }}
  </div>
  <div v-else>
    Loading...
  </div>
</template>

<script>
export default {
  data() {
    return {
      data: null,
      dataLoaded: false
    };
  },
  mounted() {
    // Simulate an asynchronous data fetch
    this.fetchData();
  },
  methods: {
    fetchData() {
      // Simulate an asynchronous data fetch (e.g., an API call)
      setTimeout(() => {
        // Once data is fetched, update the data property and set dataLoaded to true
        this.data = "Some data fetched";
        this.dataLoaded = true;
      }, 2000); // Simulating a 2-second delay for demonstration purposes
    }
  }
};
</script>

In this example, we have a dataLoaded boolean flag to indicate whether the data has been loaded.

We use v-if to conditionally render the content based on whether dataLoaded is true.

While the data is being fetched, a loading message is displayed.

Once the data is fetched successfully, dataLoaded is set to true, and the actual content is rendered.

Replace the fetchData() method with your actual data fetching logic, such as making an API call with Axios or Fetch.

Once the data is received, update the data property with the fetched data and set dataLoaded to true.

This will trigger the rendering of your component with the fetched data.

To watch the height of an element in Vue.js, you can use a combination of Vue’s reactivity system and DOM manipulation.

We can do the following:

Template

Add a reference to the element whose height you want to watch.

<template>
  <div ref="elementToWatch">
    <!-- Your content here -->
  </div>
</template>

Script

Set up a watcher to monitor changes in the height of the element.

<script>
export default {
  data() {
    return {
      elementHeight: 0
    };
  },
  mounted() {
    // Call the method to get the initial height
    this.getElementHeight();
    // Listen for resize events
    window.addEventListener('resize', this.getElementHeight);
  },
  beforeDestroy() {
    // Remove the resize event listener to prevent memory leaks
    window.removeEventListener('resize', this.getElementHeight);
  },
  methods: {
    getElementHeight() {
      // Access the element using the ref and get its height
      const element = this.$refs.elementToWatch;
      if (element) {
        this.elementHeight = element.clientHeight;
      }
    }
  }
};
</script>

Template Usage

Display or use the elementHeight variable wherever you need it in your template.

<template>
  <div>
    The height of the element is: {{ elementHeight }}px
  </div>
</template>

This approach ensures that whenever the height of the element changes (due to window resizing or dynamic content changes), the elementHeight variable is updated accordingly.

To directly change state with Vue and Vuex, we should use mutations. Mutations are synchronous functions responsible for modifying the state in a Vuex store.

To directly change state using mutations, we:

1. Define a mutation in our Vuex store.
2. Commit the mutation from our Vue components.

For example, we write

// store.js
import Vue from 'vue';
import Vuex from 'vuex';

Vue.use(Vuex);

const store = new Vuex.Store({
  state: {
    counter: 0
  },
  mutations: {
    increment(state) {
      state.counter++;
    },
    decrement(state) {
      state.counter--;
    },
    setCounter(state, value) {
      state.counter = value;
    }
  }
});

export default store;

In our Vue component:

<template>
  <div>
    <p>Counter: {{ counter }}</p>
    <button @click="increment">Increment</button>
    <button @click="decrement">Decrement</button>
    <button @click="setCounter(0)">Reset</button>
  </div>
</template>

<script>
import { mapState, mapMutations } from 'vuex';

export default {
  computed: {
    ...mapState(['counter'])
  },
  methods: {
    ...mapMutations(['increment', 'decrement', 'setCounter'])
  }
};
</script>

In this example we have a Vuex store with a counter state and mutations to increment, decrement, and set the counter.

In the Vue component, we use mapState to map the counter state from the Vuex store to a computed property.

We use mapMutations to map the mutations from the Vuex store to methods in the component.

We can then call these methods directly from the component to modify the state in the Vuex store.

By using mutations, we ensure that state changes are tracked, debuggable, and predictable.

Vuex enforces the principle of a single state tree and mutations being the only way to change the state, which helps manage state changes in a large application.