How to find the sum of elements in vue

Vue.js is a JavaScript framework that uses the MVVM pattern to build scalable web applications. Vue.js makes it easy for developers to handle interactions between data and UI, and provides many useful built-in directives and components.

In Vue.js applications, it is often necessary to perform calculations on elements in the page, such as sums, averages, etc. This article will introduce how to use Vue.js to calculate the sum of elements.

1. Data Binding

In Vue.js, use data binding to associate page elements with data in a Vue.js instance. We can use the v-model directive to bind input controls to data, and use {{}} interpolation expressions to output data to the page. For example:

<template>
  <div>
    <label>数值1:</label>
    <input type="number" v-model="num1">
    <br>
    <label>数值2:</label>
    <input type="number" v-model="num2">
    <br>
    <label>数值3:</label>
    <input type="number" v-model="num3">
    <br>
    <label>数值4:</label>
    <input type="number" v-model="num4">
    <br>
    <label>总和:</label>
    <span>{{ sum }}</span>
  </div>
</template>

<script>
export default {
  data() {
    return {
      num1: 0,
      num2: 0,
      num3: 0,
      num4: 0,
    }
  },
  computed: {
    sum() {
      return parseInt(this.num1) + parseInt(this.num2) + parseInt(this.num3) + parseInt(this.num4);
    }
  }
}
</script>

In the above code, we define a Vue.js component, which contains 4 input boxes and an output box. Each input box is bound to a data item in the Vue.js instance, and we use the computed property to calculate the sum and output the result to the page.

2. Computed properties

Computed properties are a very useful feature in Vue.js that allow us to define derived properties based on other data. Computed properties can be cached and recalculated only when the associated data changes. For attributes that frequently need to be calculated, using calculated attributes can improve performance and avoid repeated calculations. We can use computed properties to calculate the sum of elements, for example:

<template>
  <div>
    <ul>
      <li v-for="(item, index) in items" :key="index">
        {{ item }} 
      </li>
    </ul>
    <label>总和:</label>
    <span>{{ sum }}</span>
  </div>
</template>

<script>
export default {
  data() {
    return {
      items: [1, 2, 3, 4]
    }
  },
  computed: {
    sum() {
      return this.items.reduce(function (total, num) {
        return total + num;
      }, 0);
    }
  }
}
</script>

In the above code, we define an array items and use the v-for directive to render them into an unordered list. We use the computed property to calculate the sum and the reduce method to accumulate all elements in the array.

3. Usage

Computed properties are suitable for use in templates, but if we need to perform some operations in the Vue.js instance and return the calculated results, we can use method. Methods are not cached and are recalculated each time they are called, so may not be as efficient as computed properties. For example:

<template>
  <div>
    <ul>
      <li v-for="(item, index) in items" :key="index">
        {{ item }} 
      </li>
    </ul>
    <label>总和:</label>
    <span>{{ getSum() }}</span>
  </div>
</template>

<script>
export default {
  data() {
    return {
      items: [1, 2, 3, 4]
    }
  },
  methods: {
    getSum() {
      return this.items.reduce(function (total, num) {
        return total + num;
      }, 0);
    }
  }
}
</script>

In the above code, we define a method getSum(), use the reduce method to calculate the sum of elements, and call it in the template and output the result.

Conclusion

In general, you can use data binding, calculated properties and methods to find the sum of elements in a Vue.js application. Just choose the appropriate method according to the specific situation. Vue.js provides a very convenient way to handle the interaction between data and UI, allowing us to focus more on the implementation of business logic. Through the introduction of this article, I believe that readers have a deeper understanding of Vue.js to find the sum of elements.

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