vant-weapp/dist/mixins/basic.js

export const basic = Behavior({
    methods: {
        $emit(...args) {
            this.triggerEvent(...args);
        },
        set(data, callback) {
            this.setData(data, callback);
            return new Promise(resolve => wx.nextTick(resolve));
        },
        getRect(selector, all) {
            return new Promise(resolve => {
                wx.createSelectorQuery()
                    .in(this)[all ? 'selectAll' : 'select'](selector)
                    .boundingClientRect(rect => {
                    if (all && Array.isArray(rect) && rect.length) {
                        resolve(rect);
                    }
                    if (!all && rect) {
                        resolve(rect);
                    }
                })
                    .exec();
            });
        }
    }
});