What is the significance of the dollar sign prefix ($) in Vue.js?

Can you explain the significance of the dollar symbol prefix used before property names in Vue.js?

For instance, consider this code snippet: this.$emit('clicked', 'demo')

Answer №1

If you want to understand the use of the $ and _ prefixes in Vue, check out this resource:

https://v2.vuejs.org/v2/style-guide/#Private-property-names-essential

You can find detailed explanations in the section called Detailed Explanation.

The prefix _ is typically used for private instance properties in Vue components:

Vue uses the _ prefix to define its own private properties...

On the other hand, the prefix $ is usually reserved for public instance properties:

As for the $ prefix, its purpose within the Vue ecosystem is special instance properties that are exposed to the user...

These prefixes help prevent naming conflicts with properties set by component creators, like props and data properties.


The $ prefix isn't only limited to Vue's core APIs. It's also a commonly used convention in libraries that extend component functionality. For example:

  • Vuex includes $store.
  • Vue Router provides $route and $router.

These libraries are officially supported, but many third-party libraries also adopt the same convention.

In addition, application code may use the $ prefix when creating global properties. One common practice is adding $http to Vue.prototype (or globalProperties in Vue 3).

In all these scenarios, the presence of $ signifies that the property originates from an external source rather than being part of the current component itself.

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