state_management.js

let createState=(initialvalue)=>{

    let state={...initialvalue};

    let getstate=()=>({...state});


    let setstate=(input)=>{

        if(input.constructor===Object)state={...state,...input};

        if(input.constructor===Function)state={...input({...state})};

    };

return [getstate,setstate];
}
var [getState,updateState]=createState({counter:0});

getState(); //{counter: 0}

updateState((oldState)=>{oldState.counter++;return oldState;});

getState(); //{counter: 1}