var intRand = Math.random()
        var arrRand = []
        wx.getStorage({
            key: 'rand',
            success: res => {
                arrRand = res.data
            },
            complete: err => {
                arrRand.push(intRand)
                wx.setStorage({
                    key: 'rand',
                    data: arrRand,
                })
                this.showRand()
            },
        })

https://developers.weixin.qq.com/s/XL0tEkmG7afK

数组push？