VueJS - Routing

VueJS does not have a built-in router feauture. We need to follow some additional steps to install it.
The latest version of vue-router is available at  https://unpkg.com/vue-router/dist/vue-router.js
Unpkg.com provides npm-based cdn links. The above link is always updated to the recent version. We can download and host it, and use it with a script tag along with vue.js as follows −
<script src = "/path/to/vue.js"></script>
<script src = "/path/to/vue-router.js"></script>
Run the following command to install the vue-router.
npm  install vue-router
We can clone the repository from GitHub as follows −
git clone https://github.com/vuejs/vue-router.git node_modules/vue-router
cd node_modules/vue-router
npm install
npm run build
Let us start with a simple example using vue-router.js.
Example
<html>
   <head>
      <title>VueJs Instance</title>
      <script type = "text/javascript" src = "js/vue.js"></script>
      <script type = "text/javascript" src = "js/vue-router.js"></script>
   </head>
   <body>
      <div id = "app">
         <h1>Routing Example</h1>
         <p>
            <router-link to = "/route1">Router Link 1</router-link>
            <router-link to = "/route2">Router Link 2</router-link>
         </p>
         <!-- route outlet -->
         <!-- component matched by the route will render here -->
         <router-view></router-view>
      </div>
      <script type = "text/javascript">
         const Route1 = { template: '<div style = "border-radius:20px;background-color:cyan;width:200px;height:50px;margin:10px;font-size:25px;padding:10px;">This is router 1</div>' }
         const Route2 = { template: '<div style = "border-radius:20px;background-color:green;width:200px;height:50px;margin:10px;font-size:25px;padding:10px;">This is router 2</div>' }
         const routes = [
            { path: '/route1', component: Route1 },
            { path: '/route2', component: Route2 }
         ];
         const router = new VueRouter({
            routes // short for `routes: routes`
         });
         var vm = new Vue({
            el: '#app',
            router
         });
      </script>
   </body>
</html>
Output
To start with routing, we need to add the vue-router.js file. Take the code from https://unpkg.com/vue-router/dist/vue-router.js and save it in the file vue-router.js.
The script is added after vue.js as follows −
<script type = "text/javascript" src = "js/vue.js"></script>
<script type = "text/javascript" src = "js/vue-router.js"></script>
In the body section, there is a router link defined as follows −
<p>
   <router-link   to = "/route1">Router Link 1</router-link>
   <router-link    to = "/route2">Router Link 2</router-link>
</p>
<router-link> is a component used to navigate to the HTML content to be displayed to the user. The to property is the destination, i.e the source file where the contents to be displayed will be picked.
In the above piece of code, we have created two router links.
Take a look at the script section where the router is initialized. There are two constants created as follows −
const  Route1 = { template: '<div style = "border-radius:20px;background-color:cyan;width:200px;height:50px;margin:10px;font-size:25px;padding:10px;">This is router 1</div>' };
const Route2 = { template: '<div style = "border-radius:20px;background-color:green;width:200px;height:50px;margin:10px;font-size:25px;padding:10px;">This is router 2</div>' }
They have templates, which needs to be shown when the router link is clicked.
Next, is the routes const, which defines the path to be displayed in the URL.
const routes = [
   { path: '/route1', component: Route1 },
   { path: '/route2', component: Route2 }
];
Routes define the path and the component. The path i.e. /route1 will be displayed in the URL when the user clicks on the router link.
Component takes the templates names to be displayed. The path from the routes need to match with the router link to the property.
For example, <router-link  to = ”path here”></router-link>
Next, the instance is created to VueRouter using the following piece of code.
const router = new VueRouter({
   routes // short for `routes: routes`
});
The VueRouter constructor takes the routes as the param. The router object is assigned to the main vue instance using the following piece of code.
var vm = new Vue({
   el: '#app',
   router
});
Execute the example and see the display in the browser. On inspecting and checking the router link, we will find that it adds class to the active element as shown in the following screenshot.
The class added is class = “router-link-exact-active router-link-active”. The active link gets the class as shown in the above screenshot. Another thing to notice is, the <router-link> gets rendered as a tag.
Let us see some more properties to be passed to <router-link>.
This is the destination path given to the <router-link>. When clicked, the value of to will be passed to router.push() internally. The value needs to be a string or a location object. When using an object, we need to bind it as shown in e.g. 2.
e.g. 1:  <router-link to = "/route1">Router Link 1</router-link>
renders as
<a href = ”#/route”>Router Link </a>
e.g. 2:  <router-link v-bind:to = "{path:'/route1'}">Router Link 1</router-link>
e.g. 3: <router-link v-bind:to =
   "{path:'/route1', query: { name: 'Tery' }}">Router Link 1</router-link>//router link with query string.
Following is the output of e.g. 3.
In the URL path, name = Tery is a part of the query string. E.g.: http://localhost/vueexamples/vue_router.html#/route1?name = Tery
Adding replace to the router link will call the router.replace() instead of router.push(). With replace, the navigation history is not stored.
Example
<router-link v-bind:to = "{path:'/route1', query: { name: 'Tery' }}"   replace>Router Link 1</router-link>
Adding append to the <router-link><router-link> will make the path relative.
If we want to go from the router link with path /route1 to router link path /route2, it will show the path in the browser as /route1/route2.
Example
<router-link v-bind:to = "{ path: '/route1'}" append>Router Link 1</router-link>
At present <router-link> renders as a tag. In case, we want to render it as some other tag, we need to specifty the same using tag = ”tagname”;
Example
<p>
   <router-link v-bind:to = "{ path: '/route1'}" tag = "span">Router Link 1</router-link>
   <router-link v-bind:to = "{ path: '/route2'}" tag = "span">Router Link 2</router-link>
</p>
We have specified the tag as span and this is what is displayed in the browser.
The tag displayed now is a span tag. We will still see the click going as we click on the router link for navigation.
By default, the active class added when the router link is active is router-link-active. We can overwrite the class by setting the same as shown in the following code.
<style>
   ._active{
      background-color : red;
   }
</style>
<p>
   <router-link v-bind:to = "{ path: '/route1'}" active-class = "_active">Router Link 1</router-link>
   <router-link v-bind:to = "{ path: '/route2'}" tag = "span">Router Link 2</router-link>
</p>
The class used is active_class = ”_active”. This is the output displayed in the browser.
The default exactactive class applied is router-link-exact-active. We can overwrite it using exact-active-class.
Example
<p>
   <router-link v-bind:to = "{ path: '/route1'}" exact-active-class = "_active">Router Link 1</router-link>
   <router-link v-bind:to = "{ path: '/route2'}" tag = "span">Router Link 2</router-link>
</p>
This is what is displayed in the browser.
At present, the default event for router-link is click event. We can change the same using the event property.
Example
<router-link v-bind:to = "{ path: '/route1'}" event = "mouseover">Router Link 1</router-link>
Now, when we mouseover the router link, it will navigate as shown in the following browser. Mouseover on the Router link 1 and we will see the navigation changing.