What is the process of declaring a variable within a Vue template?

Question

What is the process of declaring a variable within a Vue template?

Issue

I find myself in a situation where I must temporarily hold the output of a function call in Vue templates. This is a common scenario within loops, especially when computed properties are not easily applicable.

<ul>
  <li v-for="vehicleType in vehicleTypes" :key="vehicleType">
    <h3>{{ vehicleType }}</h3>
    <div v-if="getVehicleTypeData(vehicleType)">
     {{ getVehicleTypeData(vehicleType).costPerMile }}<br>
     {{ getVehicleTypeData(vehicleType).costPerHour }}<br>
    </div>
  </li>
</ul>

Javascript code snippet:

getVehicleTypeData: function(vehicleType){
    let options = _.find(this.vehicleTypeOptions, (obj)=>{
      return obj.vehicleType==vehicleType;
    });

    return options;
}

In order to optimize performance, I am in need of a variable to cache the result of the function call.

What would be the most suitable Vue approach to address this issue?

javascript vue.js vue-component

Answer 1

Answer №1

To overcome current limitations in Vue, one workaround is to utilize scoping with v-for and a single loop. Here's an example for better understanding:

<v-list>
  <v-list-tile v-for="(module, idx) in modules">
    <template v-for="scope in [{ isLocked: someFunction(module)}]">
      <!-- any markup -->
      <v-list-tile-action v-if="scope.isLocked">
        <v-icon color="amber">lock</v-icon>
      </v-list-tile-action>
    </template>
  </v-list-tile>
</v-list>

The <template> element mentioned above is the key. By calling your function (someFunction) within a temporary array of objects, assigning it to a property (isLocked), which is then assigned to a scoped variable (scope), you can access the return value of someFunction multiple times without compromising performance using scope.isLocked.

Answer 2

To overcome current limitations in Vue, one workaround is to utilize scoping with v-for and a single loop. Here's an example for better understanding:

<v-list>
  <v-list-tile v-for="(module, idx) in modules">
    <template v-for="scope in [{ isLocked: someFunction(module)}]">
      <!-- any markup -->
      <v-list-tile-action v-if="scope.isLocked">
        <v-icon color="amber">lock</v-icon>
      </v-list-tile-action>
    </template>
  </v-list-tile>
</v-list>

The <template> element mentioned above is the key. By calling your function (someFunction) within a temporary array of objects, assigning it to a property (isLocked), which is then assigned to a scoped variable (scope), you can access the return value of someFunction multiple times without compromising performance using scope.isLocked.

Answer 3

Answer №2

You have the power to manipulate your code in any part of the template using :set="VAART = 12", and watch as the VAART variable is magically set (although it won't be reactive).

This enchanting trick has been successfully tested on VUE 3.

Answer 4

You have the power to manipulate your code in any part of the template using :set="VAART = 12", and watch as the VAART variable is magically set (although it won't be reactive).

This enchanting trick has been successfully tested on VUE 3.

Answer 5

Answer №3

To simplify the process, you can create a computed property that combines the type object with the vehiclesTypes array.

computed: {

  vehicles() {
    return this.vehicleTypes.map(vehicle => {
       return {
         value: vehicle,
         type: { ...this.getVehicleTypeData(vehicle) }
       }
    })
  }

},

methods: {
  getVehicleTypeData(vehicleType){
    let options = _.find(this.vehicleTypeOptions, (obj)=>{
      return obj.vehicleType==vehicleType;
    });

    return options;
  }
}

Then, you can implement:

<ul>
  <li v-for="vehicle of vehicles" :key="vehicle.value">
    <h3>{{ vehicle.value }}</h3>
    <div v-if="vehicle.type">
     {{ vehicle.type.costPerMile }}<br>
     {{ vehicle.type.costPerHour }}<br>
    </div>
  </li>
</ul>

If you follow this approach correctly, it should work as expected. Adjustments might be necessary depending on the actual values in vehiclesTypes.

I trust this solution will be helpful for you.

Answer 6

To simplify the process, you can create a computed property that combines the type object with the vehiclesTypes array.

computed: {

  vehicles() {
    return this.vehicleTypes.map(vehicle => {
       return {
         value: vehicle,
         type: { ...this.getVehicleTypeData(vehicle) }
       }
    })
  }

},

methods: {
  getVehicleTypeData(vehicleType){
    let options = _.find(this.vehicleTypeOptions, (obj)=>{
      return obj.vehicleType==vehicleType;
    });

    return options;
  }
}

Then, you can implement:

<ul>
  <li v-for="vehicle of vehicles" :key="vehicle.value">
    <h3>{{ vehicle.value }}</h3>
    <div v-if="vehicle.type">
     {{ vehicle.type.costPerMile }}<br>
     {{ vehicle.type.costPerHour }}<br>
    </div>
  </li>
</ul>

If you follow this approach correctly, it should work as expected. Adjustments might be necessary depending on the actual values in vehiclesTypes.

I trust this solution will be helpful for you.

Answer 7

Answer №4

To manage a value in Vue, you can define a component and pass the value as a prop for it to use in multiple ways, following the Vue approach.

Alternatively, you can wrap your function call in an array and utilize v-for to create an alias, although this method may seem like a hacky or lazy optimization.

new Vue({
  el: '#app',
  data: {
    vehicleTypes: [0, 1]
  },
  methods: {
    getVehicleTypeData(type) {
      return [{
        costPerMile: 10,
        costPerHour: 40
      }][type];
    }
  }
});

<script src="https://unpkg.com/vue@latest/dist/vue.js"></script>
<ul id="app" new>
  <li v-for="vehicleType in vehicleTypes" :key="vehicleType">
    <h3>{{ vehicleType }}</h3>
    <template v-for="data in [getVehicleTypeData(vehicleType)]">
      <div v-if="data">
       {{ data.costPerMile }}<br> {{ data.costPerHour }}<br>
      </div>
    </template>
  </li>
</ul>

Answer 8

To manage a value in Vue, you can define a component and pass the value as a prop for it to use in multiple ways, following the Vue approach.

Alternatively, you can wrap your function call in an array and utilize v-for to create an alias, although this method may seem like a hacky or lazy optimization.

new Vue({
  el: '#app',
  data: {
    vehicleTypes: [0, 1]
  },
  methods: {
    getVehicleTypeData(type) {
      return [{
        costPerMile: 10,
        costPerHour: 40
      }][type];
    }
  }
});

<script src="https://unpkg.com/vue@latest/dist/vue.js"></script>
<ul id="app" new>
  <li v-for="vehicleType in vehicleTypes" :key="vehicleType">
    <h3>{{ vehicleType }}</h3>
    <template v-for="data in [getVehicleTypeData(vehicleType)]">
      <div v-if="data">
       {{ data.costPerMile }}<br> {{ data.costPerHour }}<br>
      </div>
    </template>
  </li>
</ul>

Answer 9

Answer №5

After conducting thorough research, I was able to find a solution to my problem. Although I have posted the answer myself, I am unsure if there are better solutions available.

Here is the Javascript snippet:

const Pass = {
  render() {
    return this.$scopedSlots.default(this.$attrs)
  }
}

export default {
  components: {
    Pass
  },
  data: function () {
    return {
      vehicleTypeOptions: [],
    }
  },
  methods: {
    getVehicleData: function(vehicleType){
      let option = _.find(this.vehicleTypeOptions, (obj)=> {
        return obj.vehicleType == vehicleType;
      });
      return option;
    },
    loadData: function(){
      // Fetch data from server using API and populate vehicleTypeOptions
    }
  },
  mounted: function(){
    this.loadData();
  }
}

And here is the Template snippet:

<Pass v-for="vehicleType in VehicleTypes" v-bind:key="vehicleType" :temp="getVehicleData(vehicleType)">
  <div slot-scope="{temp}">
    <div class="panel">
        <h6>{{ vehicleType }}</h6>
        <p v-if="temp">
          Cost per mile: <strong>${{ temp.costPerMile }}</strong>, 
          Cost per hour: <strong>${{ temp.costPerHour }}</strong>, 
          Cost per day: <strong>${{ temp.costPerDay }}</strong>
        </p>
    </div>
  </div>
</Pass>

Answer 10

After conducting thorough research, I was able to find a solution to my problem. Although I have posted the answer myself, I am unsure if there are better solutions available.

Here is the Javascript snippet:

const Pass = {
  render() {
    return this.$scopedSlots.default(this.$attrs)
  }
}

export default {
  components: {
    Pass
  },
  data: function () {
    return {
      vehicleTypeOptions: [],
    }
  },
  methods: {
    getVehicleData: function(vehicleType){
      let option = _.find(this.vehicleTypeOptions, (obj)=> {
        return obj.vehicleType == vehicleType;
      });
      return option;
    },
    loadData: function(){
      // Fetch data from server using API and populate vehicleTypeOptions
    }
  },
  mounted: function(){
    this.loadData();
  }
}

And here is the Template snippet:

<Pass v-for="vehicleType in VehicleTypes" v-bind:key="vehicleType" :temp="getVehicleData(vehicleType)">
  <div slot-scope="{temp}">
    <div class="panel">
        <h6>{{ vehicleType }}</h6>
        <p v-if="temp">
          Cost per mile: <strong>${{ temp.costPerMile }}</strong>, 
          Cost per hour: <strong>${{ temp.costPerHour }}</strong>, 
          Cost per day: <strong>${{ temp.costPerDay }}</strong>
        </p>
    </div>
  </div>
</Pass>

Answer 11

Answer №6

Regrettably, the current version does not support this feature.

However, you can create a computed property with calculated values and utilize it in your code.

<ul>
  <li v-for="carType, index in carTypes" :key="carType">
    <h3>{{ carType }}</h3>
    <div v-if="ctData[index]">
     {{ ctData[index].pricePerMile }}<br>
     {{ ctData[index].pricePerHour }}<br>
    </div>
  </li>
</ul>

...

computed: {
  ctData() {
    return this.carTypes.map(ct => this.getCarTypeData(ct));
  }
}

Answer 12

Regrettably, the current version does not support this feature.

However, you can create a computed property with calculated values and utilize it in your code.

<ul>
  <li v-for="carType, index in carTypes" :key="carType">
    <h3>{{ carType }}</h3>
    <div v-if="ctData[index]">
     {{ ctData[index].pricePerMile }}<br>
     {{ ctData[index].pricePerHour }}<br>
    </div>
  </li>
</ul>

...

computed: {
  ctData() {
    return this.carTypes.map(ct => this.getCarTypeData(ct));
  }
}

Answer 13

Answer №7

Fernando Cesar has brought up an interesting point about the undocumented feature :set, along with a code snippet and some resources to check out.

<ul>
  <li v-for="vehicleType in vehicleTypes" 
    :key="vehicleType"
    :set="vtd = getVehicleTypeData(vehicleType)"
  >
    <h3>{{ vehicleType }}</h3>
    <div v-if="vtd">
     {{ vtd.costPerMile }}<br>
     {{ vtd.costPerHour }}<br>
    </div>
  </li>
</ul>

Check out this link for more information. You can also visit this resource for further insights.

Answer 14

Fernando Cesar has brought up an interesting point about the undocumented feature :set, along with a code snippet and some resources to check out.

<ul>
  <li v-for="vehicleType in vehicleTypes" 
    :key="vehicleType"
    :set="vtd = getVehicleTypeData(vehicleType)"
  >
    <h3>{{ vehicleType }}</h3>
    <div v-if="vtd">
     {{ vtd.costPerMile }}<br>
     {{ vtd.costPerHour }}<br>
    </div>
  </li>
</ul>

Check out this link for more information. You can also visit this resource for further insights.

Answer 15

Answer №8

One possible approach that seems trustworthy:

<template>
  <div :style="{ display: 'none', visibility: 'hidden' }">{{ count = 0 }}</div>
  {{ count }}
</template>

<script>
export default {
  mounted () {
    // The count variable is successfully initialized within the component.
    console.log(this.count)
  }
}
</script>

There may be a method for declaring variables in template iterations as well.

Answer 16

One possible approach that seems trustworthy:

<template>
  <div :style="{ display: 'none', visibility: 'hidden' }">{{ count = 0 }}</div>
  {{ count }}
</template>

<script>
export default {
  mounted () {
    // The count variable is successfully initialized within the component.
    console.log(this.count)
  }
}
</script>

There may be a method for declaring variables in template iterations as well.

Answer 17

Answer №9

An easy and secure method is to utilize a renderless component that stores your value.

// temp-var.ts
import { defineComponent } from 'vue';

const TempVar = defineComponent(
  (props, ctx) => () => ctx.slots.default?.(ctx.attrs),
  { inheritAttrs: false },
) as unknown as new <T>(props: T) => {
  $props: T;
  $slots: { default?: (context: T) => unknown };
};

export default TempVar;

Implement it in this manner: https://play.vuejs.org/#eNqVVE...

Answer 18

An easy and secure method is to utilize a renderless component that stores your value.

// temp-var.ts
import { defineComponent } from 'vue';

const TempVar = defineComponent(
  (props, ctx) => () => ctx.slots.default?.(ctx.attrs),
  { inheritAttrs: false },
) as unknown as new <T>(props: T) => {
  $props: T;
  $slots: { default?: (context: T) => unknown };
};

export default TempVar;

Implement it in this manner: https://play.vuejs.org/#eNqVVE...

Answer 19

Answer №10

Is the :set Hack Reliable? Although the :set hack may appear useful, it deviates from the Vue.js API and can result in non-reactive variables, contradicting Vue's reactive principles. This could potentially disrupt the consistency and timeliness of the user interface.

Answer 20

Is the :set Hack Reliable? Although the :set hack may appear useful, it deviates from the Vue.js API and can result in non-reactive variables, contradicting Vue's reactive principles. This could potentially disrupt the consistency and timeliness of the user interface.

What is the process of declaring a variable within a Vue template?

Answer №1

Answer №2

Answer №3

Answer №4

Answer №5

Answer №6

Answer №7

Answer №8

Answer №9

Answer №10

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