Debouncing issue in Vuejs 2 when using watch option

Question

Debouncing issue in Vuejs 2 when using watch option

After adding a debounce function in VueJs, I noticed that it works perfectly when passing the number of milliseconds directly. However, if I use a reference to a prop, it seems to be ignored.

Here's a summary of the props:

props : {
    debounce : {
        type : Number,
        default : 500
    }
}

Below is the watch option causing issues:

watch : {
    term : _.debounce(function () {
        console.log('Debounced term: ' + this.term);
    }, this.debounce)
}

And here is an alternative watch option that works without any problems:

watch : {
    term : _.debounce(function () {
        console.log('Debounced term: ' + this.term);
    }, 500)
}

I have a feeling that it could be related to a scope problem, but I'm uncertain about how to resolve it. When I modify the watch method as shown below:

watch : {
    term : function () {
        console.log(this.debounce);
    }
}

I can see the correct debounce value (500) displaying in the console.

javascript vue.js vuejs2 debouncing

Answer 1

Answer №1

One way to enhance @Bert's solution is by constructing the watcher's function within the created() method.

// Check out this Vuejs 2 example on debounce functionality with watch option

console.clear()

Vue.component("debounce",{
  props : {
    debounce : {
      type : Number,
      default : 500
    }
  },
  template:`
    <div>
      <input type="text" v-model="term">
    </div>
  `,
  data(){
    return {
      term: "",
      debounceFn: null
    }
  },
  created() {
    this.debounceFn = _.debounce( () => {
      console.log('Debounced term: ' + this.term);
    }, this.debounce)
  },
  watch : {
    term : function () {
      this.debounceFn();
    }
  },
})

new Vue({
  el: "#app"
})

<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.3/vue.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"></script>
<div id="app">
  <debounce :debounce="2000"></debounce>
</div>

Discover this code snippet live on CodePen

Answer 2

One way to enhance @Bert's solution is by constructing the watcher's function within the created() method.

// Check out this Vuejs 2 example on debounce functionality with watch option

console.clear()

Vue.component("debounce",{
  props : {
    debounce : {
      type : Number,
      default : 500
    }
  },
  template:`
    <div>
      <input type="text" v-model="term">
    </div>
  `,
  data(){
    return {
      term: "",
      debounceFn: null
    }
  },
  created() {
    this.debounceFn = _.debounce( () => {
      console.log('Debounced term: ' + this.term);
    }, this.debounce)
  },
  watch : {
    term : function () {
      this.debounceFn();
    }
  },
})

new Vue({
  el: "#app"
})

<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.3/vue.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"></script>
<div id="app">
  <debounce :debounce="2000"></debounce>
</div>

Discover this code snippet live on CodePen

Answer 3

Answer №2

The main issue at hand revolves around the usage of this.debounce as the interval when defining the debounced function. When _.debounce(...) is executed (during the compilation of the component), the function is not yet linked to Vue, resulting in this not referencing Vue and thus this.debounce being undefined. To rectify this, it's essential to set up the watch after the component instance is created. Vue offers a solution for this through the utilization of $watch.

My recommendation would be to implement this within the created lifecycle hook.

created(){
  this.unwatch = this.$watch('term', _.debounce((newVal) => {
     console.log('Debounced term: ' + this.term);
  }, this.debounce))
},
beforeDestroy(){
  this.unwatch()
}

Note that the code also contains a call to unwatch before the destruction of the component. While Vue typically manages this process automatically, manually adding the watch requires manual removal as well. Naturally, unwatch needs to be included as a data property.

Below is an illustration of how this works in action.

console.clear()

Vue.component("debounce",{
  props : {
    debounce : {
      type : Number,
      default : 500
    }
  },
  template:`
    <input type="text" v-model="term">
  `,
  data(){
    return {
      unwatch: null,
      term: ""
    }
  },
  created(){
    this.unwatch = this.$watch('term', _.debounce((newVal) => {
      console.log('Debounced term: ' + this.term);
    }, this.debounce))
  },
  beforeDestroy(){
    this.unwatch()
  }
})

new Vue({
  el: "#app"
})

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"></script>
<script src="https://unpkg.com/<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="c7b1b2a287f5e9f3e9f5">[email protected]</a>"></script>
<div id="app">
  <debounce :debounce="250"></debounce>
</div>

Answer 4

The main issue at hand revolves around the usage of this.debounce as the interval when defining the debounced function. When _.debounce(...) is executed (during the compilation of the component), the function is not yet linked to Vue, resulting in this not referencing Vue and thus this.debounce being undefined. To rectify this, it's essential to set up the watch after the component instance is created. Vue offers a solution for this through the utilization of $watch.

My recommendation would be to implement this within the created lifecycle hook.

created(){
  this.unwatch = this.$watch('term', _.debounce((newVal) => {
     console.log('Debounced term: ' + this.term);
  }, this.debounce))
},
beforeDestroy(){
  this.unwatch()
}

Note that the code also contains a call to unwatch before the destruction of the component. While Vue typically manages this process automatically, manually adding the watch requires manual removal as well. Naturally, unwatch needs to be included as a data property.

Below is an illustration of how this works in action.

console.clear()

Vue.component("debounce",{
  props : {
    debounce : {
      type : Number,
      default : 500
    }
  },
  template:`
    <input type="text" v-model="term">
  `,
  data(){
    return {
      unwatch: null,
      term: ""
    }
  },
  created(){
    this.unwatch = this.$watch('term', _.debounce((newVal) => {
      console.log('Debounced term: ' + this.term);
    }, this.debounce))
  },
  beforeDestroy(){
    this.unwatch()
  }
})

new Vue({
  el: "#app"
})

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"></script>
<script src="https://unpkg.com/<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="c7b1b2a287f5e9f3e9f5">[email protected]</a>"></script>
<div id="app">
  <debounce :debounce="250"></debounce>
</div>

Answer 5

Answer №3

To ensure that the debounced method is consistently called every time the watch is triggered, it needs to be abstracted. If we embed the debounced function within a Vue computed or watch property, it will reset on each trigger event.

const debouncedGetData = _.debounce(getData, 1000);

function getData(val){
  this.newFoo = val;
}

new Vue({
  el: "#app",
  template: `
    <div>
      <input v-model="foo" placeholder="Type something..." />
      <pre>{{ newFoo }}</pre>
    </div>
`,
    data(){
      return {
        foo: '',
        newFoo: ''
      }
    },
    watch:{
      foo(val, prevVal){
        debouncedGetData.call(this, val);
      }
    }
  
  })

<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.9.1/underscore-min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>

<div id="app"></div>

Best of luck...

Answer 6

To ensure that the debounced method is consistently called every time the watch is triggered, it needs to be abstracted. If we embed the debounced function within a Vue computed or watch property, it will reset on each trigger event.

const debouncedGetData = _.debounce(getData, 1000);

function getData(val){
  this.newFoo = val;
}

new Vue({
  el: "#app",
  template: `
    <div>
      <input v-model="foo" placeholder="Type something..." />
      <pre>{{ newFoo }}</pre>
    </div>
`,
    data(){
      return {
        foo: '',
        newFoo: ''
      }
    },
    watch:{
      foo(val, prevVal){
        debouncedGetData.call(this, val);
      }
    }
  
  })

<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.9.1/underscore-min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>

<div id="app"></div>

Best of luck...

Answer 7

Answer №4

Setting up a new Vue instance with debounce functionality for handling user input:

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.3/vue.js"></script>
<div id="term">
  <input v-model="term">
</div>

Answer 8

Setting up a new Vue instance with debounce functionality for handling user input:

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.3/vue.js"></script>
<div id="term">
  <input v-model="term">
</div>

Debouncing issue in Vuejs 2 when using watch option

Answer №1

Answer №2

Answer №3

Answer №4

Similar questions

Every time I attempt to run "npm install" on Visual Studio Code, I encounter an error

Encountering an "Unknown Provider" issue while trying to inject a provider from another module into a

The arrow icon for selecting input in Material Dashboard React is missing

Maximizing the Efficiency of jQuery and Javascript Frameworks

The functionality of the Node.js/Express.js app is limited to operating solely on Port 3000

What is your approach to converting this jQuery code to ES6 syntax?

Merging two arrays that have identical structures

Control the line height in DataTables

Top tips for data manipulation

Modify the text tone within a specific cell

Creating a vertical slider with an unordered list

Encountering an error while trying to install the VUE CLI using the npm command with the message "

Issue with window resize directive not functioning as expected

Synchronize information between mongoDB and firebase bidirectionally

Standardize all values for each key in sub-dictionaries and include them as additional key-value pairs

Verify if a string containing only numerical values contains any non-numeric characters

Changing the formatting of a buffer from int8 to float32 using JavaScript

Oops! We encountered an issue with this dependency being missing - TypeScript and Vue

Utilizing Array Filters and State in React JS to Conceal Table Columns

Can you provide instructions on executing package dependencies using yarn in the command line? For example, is there a command similar to npx tsc init for initializing a npm