Can I pass parameters in computed properties in Vue.Js

You can use methods, but I prefer still to use computed properties instead of methods, if they're not mutating data or do not have external effects.

You can pass arguments to computed properties this way (not documented, but suggested by maintainers, don't remember where):

computed: {
   fullName: function () {
      var vm = this;
      return function (salut) {
          return salut + ' ' + vm.firstName + ' ' + vm.lastName;  
      };
   }
}

EDIT: Please do not use this solution, it only complicates code without any benefits.

Most probably you want to use a method

<span>{{ fullName('Hi') }}</span>

methods: {
  fullName(salut) {
      return `${salut} ${this.firstName} ${this.lastName}`
  }
}

---

Longer explanation

Technically you can use a computed property with a parameter like this:

computed: {
   fullName() {
      return salut => `${salut} ${this.firstName} ${this.lastName}`
   }
}

(Thanks Unirgy for the base code for this.)

The difference between a computed property and a method is that computed properties are cached and change only when their dependencies change. A method will evaluate every time it's called.

If you need parameters, there are usually no benefits of using a computed property function over a method in such a case. Though it allows you to have a parametrized getter function bound to the Vue instance, you lose caching so not really any gain there, in fact, you may break reactivity (AFAIU). You can read more about this in Vue documentation https://v2.vuejs.org/v2/guide/computed.html#Computed-Caching-vs-Methods

The only useful situation is when you have to use a getter and need to have it parametrized. For instance, this situation happens in Vuex. In Vuex it's the only way to synchronously get parametrized result from the store (actions are async). Thus this approach is listed by official Vuex documentation for its getters https://vuex.vuejs.org/guide/getters.html#method-style-access