In the ready: method of the root instance, I have certain tasks to perform but only if some components are not present (not declared in the HTML).
Is there a way to verify the existence of a component?
In the ready: method of the root instance, I have certain tasks to perform but only if some components are not present (not declared in the HTML).
Is there a way to verify the existence of a component?
One way to retrieve the list of loaded components in a Vue instance is by accessing the instantiation options via the vm.$options. This property contains all the information about the Vue instance, including its components.
The vm.$options.components property specifically holds the loaded components of the current Vue instance. Depending on whether a component is registered globally using Vue.component() or locally within the instance options, the structure of this property may vary.
When a component is globally registered, it is linked to vm.$options.components through its [[Prototype]] or __proto__.
On the other hand, if a component is locally registered within the Vue instance options, it is directly added to the vm.$options.components object as its own property. This simplifies the process of accessing the component without traversing the prototype chain.
In the example below, we demonstrate how to access loaded components in both scenarios.
Pay attention to the // [1] and // [2] comments in the code, which relate to locally registered components.
// Example showcasing global and local component registration
Vue.component('global-child', {
template: '<h2>A message from the global component</h2>'
});
var localComponent = Vue.extend({ template: '<h2>A message from the local component</h2>' });
// Define the root Vue instance
new Vue({
el: 'body',
data: {
allComponents: [],
localComponents: [],
globalComponentIsLoaded: false
},
// Register local components
components: { // [1]
'local-child': localComponent
},
ready: function() {
this.localComponents = Object.keys(this.$options.components); // [2]
this.allComponents = getLoadedComponents.call(this);
this.globalComponentIsLoaded = checkIfComponentExists.call(this, 'global-child');
}
});
function getLoadedComponents() {
var loaded = [];
var components = this.$options.components;
for (var key in components) {
loaded.push(key);
}
return loaded;
}
function checkIfComponentExists(component) {
var components = getLoadedComponents.call(this);
if (components.indexOf(component) !== -1) {
return true;
}
return false;
}<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/1.0.24/vue.js"></script>
<h1>Message from the root Vue instance</h1>
<p>All loaded components: {{ allComponents | json }}</p>
<p>Local components: {{ localComponents | json }}</p>
<p><code><global-child></code> component loaded: <strong>{{ globalComponentIsLoaded }}</strong></p>
<global-child></global-child>
<local-child></local-child>If you are unsure about the necessity of a dynamic approach, you can use this code snippet to check for the existence of a component:
Vue.options.components['CompOne']
More information can be found at:
One way to verify the presence of a global component:
const isGlobalComponent = 'componentName' in Vue.options.components
To confirm the existence of an imported component within a specific component:
const isImportedComponent = 'componentName' in this.$options.components
retrieve the components that are currently imported in the component
this.$options.components[findComponentName]
fetch all the globally available components in Vue
Vue.$options.components[findComponentName]
let checkComponent = "component-name" in Vue.options.components
While I am hopeful for a more optimal solution, the current approach effectively resolves the issue at hand.
During initialization, I iterate through the child elements using this (or possibly Vue) to verify if their names match my expectations:
ready: function() {
for (var i = 0; i < this.$children.length; i++) {
if (
this.$children[i].$options.name == 'my_component_a'
|| this.$children[i].$options.name == 'my_component_b'
|| this.$children[i].$options.name == 'my_component_c'
) {
//perform actions
}
}
}
If you have assigned a reference in the template, you can directly access them as well: //template:
<comp v-ref:my_component_ref></comp>
Then within the Vue component's ready function:
if (this.$refs.my_component_ref){
//perform actions
}
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