vant-weapp/packages/button/index.js

const nativeBehaviors = require('./behaviors');
const classnames = require('../common/classnames');

const observer = function () {
  this.setClasses();
};

Component({
  externalClasses: ['custom-class'],

  behaviors: [nativeBehaviors],

  properties: {
    type: {
      type: String,
      value: 'default',
      observer
    },
    size: {
      type: String,
      value: 'normal',
      observer
    },
    plain: {
      type: Boolean,
      value: false,
      observer
    },
    disabled: {
      type: Boolean,
      value: false,
      observer
    },
    loading: {
      type: Boolean,
      value: false,
      observer
    },
    block: {
      type: Boolean,
      value: false,
      observer
    }
  },

  data: {
    classes: ''
  },

  attached() {
    this.setClasses();
  },

  methods: {
    onTap(event) {
      if (!this.data.disabled && !this.data.loading) {
        this.triggerEvent('click', event);
      }
    },

    setClasses() {
      const { type, size, plain, disabled, loading, block } = this.data;
      this.setData({
        classes: classnames(
          `van-button--${type}`,
          `van-button--${size}`,
          {
            'van-button--block': block,
            'van-button--plain': plain,
            'van-button--loading': loading,
            'van-button--disabled': disabled,
            'van-button--unclickable': disabled || loading
          }
        )
      });
    }
  }
});