Vue-Multiselect | Vue Select Library
vue-multiselect.js.orgVue-Multiselect supports changing the option list on the fly, thus can be also used a type-a-head search box. To react to the search query changes, set a handler function on the @search-change event. It receives the searchQuery as the first param, which can be used to make an asynchronous API call.
vue.js - Vue-MultiSelect Checkbox binding - Stack Overflow
In your code you call onSelect and try to change the option argument of this function inside the function: option.checked = true; This affects only the local variable option (the function argument). And doesn't affect objects in options array in the data of the Vue instance, the objects bound with checkboxes.