resize.vue

<template>
  <div>
    <div :class="isSmall ? 'small' : 'large'"
         @click="resize()"
         class="other-styles"></div>
    <div class="other-styles"></div>
    <div class="other-styles"></div>
    <div class="other-styles"></div>
  </div>
</template>

<script>
export default {
  name: "Foo",
  data: function () {
    return {
      isSmall: false
    };
  },
  methods: {
    resize () {
      this.isSmall = !this.isSmall;
    }
  }
};
</script>

<style scoped>

.small {
  width: 100px;
}

.large {
  width: 500px;
}

.other-styles {
  background-color: blue;
}

</style>