Vue

by WILLIAM CORREA

HTML

<div id="app">
  <input type="text" v-model="extra"> <input type="number" v-model="maxLength">
  <hr>
  <input type="text" @keydown="keydown" :maxlength="maxLength">
</div>

CSS

body {
  background: #20262E;
  padding: 20px;
  font-family: Helvetica;
}

#app {
  background: #fff;
  border-radius: 4px;
  padding: 20px;
  transition: all 0.2s;
}

li {
  margin: 8px 0;
}

h2 {
  font-weight: bold;
  margin-bottom: 15px;
}

del {
  color: rgba(0, 0, 0, 0.3);
}

Vue

new Vue({
  el: "#app",
  props: {
  	maxLength: {
    	type: Number,
      default: 4
    },
    expression: {
    	type: String,
      default: '^[\\d]|Backspace|Enter|Arrow.*|Shift|Home|End'
    }
  },
  data: 
  methods: {
  	keydown ($event) {
    	if ((new RegExp(this.expression)).test($event.key)) {
      	return
      }
      $event.preventDefault()
    }
  }
})