[Vuejs]-@property in vue components

It’s just documenting the component arguments/properties.

From the docunentation:

 If your event returns arguments/properties use the @property tag to describe them

/**
 * Triggers when the number changes
 *
 * @property {number} newValue new value set
 * @property {number} oldValue value that was set before the change
 */

this.$emit('change', newValue, oldValue)