vant/src/number-keyboard/Key.js

import { createNamespace } from '../utils';
import { TouchMixin } from '../mixins/touch';
import { BORDER } from '../utils/constant';

const [createComponent, bem] = createNamespace('key');

export default createComponent({
  mixins: [TouchMixin],

  props: {
    type: String,
    text: [Number, String],
    theme: {
      type: Array,
      default: () => []
    }
  },

  data() {
    return {
      active: false
    };
  },

  computed: {
    className() {
      const classNames = this.theme.slice(0);

      if (this.active) {
        classNames.push('active');
      }

      if (this.type) {
        classNames.push(this.type);
      }

      return bem(classNames);
    }
  },

  methods: {
    onTouchStart(event) {
      // compatible with Vue 2.6 event bubble bug
      event.stopPropagation();

      this.touchStart(event);
      this.active = true;
    },

    onTouchMove(event) {
      this.touchMove(event);

      if (this.direction) {
        this.active = false;
      }
    },

    onTouchEnd() {
      if (this.active) {
        this.active = false;
        this.$emit('press', this.text, this.type);
      }
    }
  },

  render() {
    return (
      <i
        role="button"
        tabindex="0"
        class={[BORDER, this.className]}
        onTouchstart={this.onTouchStart}
        onTouchmove={this.onTouchMove}
        onTouchend={this.onTouchEnd}
        onTouchcancel={this.onTouchEnd}
      >
        {this.slots('default') || this.text}
      </i>
    );
  }
});