随机生成RGB三原色

    getRandomColor: function() {
                const rgb = []
                for (let i = 0; i < 3; ++i) {
                    let color = Math.floor(Math.random() * 256).toString(16)
                    color = color.length == 1 ? '0' + color : color
                    rgb.push(color)
                }
                return '#' + rgb.join('')
            }