//In TypeScript there are no 
//structures with type members
class Setting { 
    //type field
    static mode: number

    //type method
    static setNextMode() {
        Setting.mode = (Setting.mode + 1) % 3
    }
}

Setting.mode = 3
Setting.setNextMode()
//Setting.mode is 1

console.log("mode is", Setting.mode)