Vue

HTML

<div id="app">
   <form v-on:submit.prevent="submit" id="email-form" action="/signup" method="POST">
     <input id="email" type="text" v-model="email" />
     <input type="submit" value="Signup for our emails!"/>
   </form>
</div>

Vue

new Vue({
  el: "#app",
  data: {
  	email: ""
  },
  methods: {
  	submit() {
			if (this.validate()) {
      	alert("Do Request!")
      }
    },
    validate() {
    	if (this.email === "") {
      	alert("Enter an email address!")
      }
    
    	return this.email !== ""
    }
  }
})