Vue 2.5 shipped significant TypeScript improvements and a new error handling hook. Here's what changed.

Better TypeScript Support with Vue.extend

// Before 2.5: using vue-class-component decorator syntax
import Vue from "vue";
import Component from "vue-class-component";

@Component({
  template: '<button @click="onClick">Click!</button>',
})
class MyComponent extends Vue {
  message: string = "Hello!";
  onClick() {
    window.alert(this.message);
  }
}

// Vue 2.5+: Vue.extend works better with TypeScript
import Vue from "vue";

const MyComponent = Vue.extend({
  data() {
    return {
      message: "Hello!" as string,
    };
  },
  methods: {
    greet(): void {
      console.log(this.message); // correctly typed
    },
  },
});

The type inference in Vue.extend() is significantly improved: this.message, this.$data, and this.$store all have correct types without decorators.

Functional Component Improvements

Functional components (stateless, no this) got better TypeScript support:

// Functional component with TypeScript
import { FunctionalComponentOptions } from "vue";

const FancyList: FunctionalComponentOptions = {
  functional: true,
  props: {
    items: Array,
  },
  render(createElement, context) {
    return createElement(
      "ul",
      context.props.items.map((item) => createElement("li", item.name)),
    );
  },
};

errorCaptured Hook

Vue 2.5 introduced errorCaptured — the Vue equivalent of React's Error Boundaries:

export default {
  name: "ErrorWrapper",
  data() {
    return { error: null };
  },
  errorCaptured(err, vm, info) {
    // err: the error object
    // vm: the component that threw
    // info: a string describing where the error was caught
    this.error = err.message;
    // Return false to prevent the error from propagating further
    return false;
  },
};

Usage:

<template>
  <div>
    <div v-if="error" class="error-display">Component error: {{ error }}</div>
    <slot v-else />
  </div>
</template>

The error propagates up the component tree until a component with errorCaptured returns false.

v-on Multiple Event Listeners

<!-- Before 2.5: repeated v-on -->
<input v-on:focus="onFocus" v-on:blur="onBlur" v-on:input="onInput" />

<!-- Vue 2.5+: v-on with object syntax -->
<input v-on="{ focus: onFocus, blur: onBlur, input: onInput }" />

This is particularly useful when building higher-order components that need to pass through all event listeners.