Vue is prone to errors

Vue is a popular JavaScript framework that uses a simple and easy-to-use programming model to help developers build dynamic web applications. Vue can provide better organization structure, maintainability and testability during the development process, but there are still some error-prone points in the process of using Vue. This article will discuss these error-prone points and their solutions to help you use Vue more efficiently.

1. The template was written without using "v-bind" or the abbreviation symbol

When using Vue, the template system usually handles interpolation and property binding automatically. For example, the following code:

<div class="mycomponent" :title="mytitle">{{ message }}</div>

will bind the value of the variable mytitle to the title attribute of the element and the variable message The value is inserted into the element's text content.

However, it is possible to bind a property without using it before v-bind or the abbreviation notation :. The following code:

<input type="text" value="{{ message }}">

does not produce the expected results. Instead, it should be written like this:

<input type="text" :value="message">

2. Reference to data object

Vue's data A property in an object should not be the same as another object reference . For example, the following code:

var data = { message: 'Hello' };
new Vue({ data: data });

Later in the code, data.message can be modified, but it will not be reflected in the application. This is because the data object has been wrapped once by Vue before being passed to the Vue constructor, which means we are modifying an ignored copy object instead of the data# in the Vue instance ## Object.

The solution is to create a new

data object for each Vue instance.

new Vue({ data: { message: 'Hello' }});

Confusion of computed properties and methods

Computed properties and methods in Vue are two different things. The difference is that computed properties are based on dependency caching of. That is, computed properties are only called when dependencies change. Instead, the method is called on every access.

If no dependencies are used in a Vue template, Vue will not detect "triggers" that should recalculate computed properties.

The workaround is to make sure the computed property is defined as a function with dependencies. Even if dependencies are dynamic, you can use functions to return them.

Component data sharing issue

When passing objects or arrays through

props, if you change the properties of one of the objects or arrays, Vue will not Changes are detected because it only tracks passed references. This may cause unexpected side effects.

The solution is to make sure not to directly change the object or array passed by the parent component in the child component. If you must change, you can use the

Object.assign() or Array.prototype.slice() method to generate a new object or array.

// 父组件
<template>
  <child-component :data="data"></child-component>
</template>

<script>
export default {
  data() {
    return {
      data: { message: 'Hello' }
    }
  }
}
</script>

// 子组件
<template>
  <div>{{ data.message }}</div>
</template>

<script>
export default {
  props: ['data'],
  created() {
    // 以下代码将会更改祖先组件中的 "data" 对象
    this.data.message = 'Changed';
  }
}
</script>

// 正确的写法
<template>
  <div>{{ localData.message }}</div>
</template>

<script>
export default {
  props: ['data'],
  data() {
    return { localData: Object.assign({}, this.data) }
  },
  created() {
    this.localData.message = 'Changed';
  }
}
</script>

Problems with asynchronous components

Vue provides the function of asynchronous component loading, which can be used to delay loading components to optimize application performance. However, during development such components may cause some problems. For example, if the parent component has finished rendering and started executing before the component's asynchronous loading is completed, the child component will not render correctly.

The solution is to use the

loading option of the asynchronous component in the child component. loading option can display a placeholder before the component is rendered.

Vue.component('my-component', function(resolve) {
  setTimeout(function() {
    resolve({
      template: '<div>Hello</div>'
    });
  }, 1000);
});

<template>
  <div>
    <my-component v-if="showComponent" />
    <div v-else>Loading...</div>
  </div>
</template>

<script>
export default {
  data() {
    return { showComponent: false }
  },
  components: {
    'my-component': () => import('./MyComponent.vue'),
  },
  created() {
    setTimeout(() => this.showComponent = true, 1000)
  }
}
</script>

Summary

Vue is a powerful framework that can help us build web applications more efficiently. However, when using Vue, we need to pay attention to some error-prone points to ensure that the functions provided by the framework are used correctly. In this article, we discuss some common error-prone points and solutions, hoping to help you in the process of using Vue.

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