small functions

var array=[{"name":"Import danych do bazy danych","start_time":"2019-05-08","end_time":"2019-05-10","status":"new","parent_id":34,"id":36,"assignee":"Bartłomiej Nowak"},{"name":"Utworzenie modeli bazy danych","start_time":"2019-05-07","end_time":"2019-05-08","status":"new","parent_id":34,"id":35,"assignee":"Justyna Malik"},{"name":"Utworzenie repozytorium git","start_time":"2019-05-06","end_time":"2019-05-06","status":"new","parent_id":29,"id":33,"assignee":"Justyna Malik"},{"name":"Sortowanie bąbelkowe","start_time":"2019-05-01","end_time":"2019-05-02","status":"completed","parent_id":10,"id":11,"assignee":"Jan Kowalski"},{"name":"Sortowanie przez scalanie","start_time":"2019-05-02","end_time":"2019-05-03","status":"pending","parent_id":10,"id":12,"assignee":"Jan Kowalski"},{"name":"Sortowanie mergsort","start_time":"2019-05-04","end_time":"2019-05-05","status":"new","parent_id":10,"id":14,"assignee":"Bartłomiej Nowak"},{"name":"Migracja systemu zadań","start_time":"2019-05-06","end_time":"2019-05-24","status":"new","parent_id":"","id":29,"assignee":"Jan Kowalski"},{"name":"Wyświetlanie zadań na osi czasu","start_time":"2019-05-07","end_time":"2019-05-10","status":"new","parent_id":"29","id":32,"assignee":"Bartłomiej Nowak"},{"name":"Sortowanie zadań wg. czasu wykonania","start_time":"2019-05-06","end_time":"2019-05-07","status":"new","parent_id":29,"id":31,"assignee":"Bartłomiej Nowak"},{"name":"Utowrzenie endpointów dla aplikacji web","start_time":"2019-05-10","end_time":"2019-05-10","status":"new","parent_id":34,"id":"37","assignee":"Justyna Malik"},{"name":"Sortowanie quicksort","start_time":"2019-05-03","end_time":"2019-05-04","status":"new","parent_id":10,"id":13,"assignee":"Bartłomiej Nowak"},{"name":"Integracja z Django","start_time":"2019-05-07","end_time":"2019-05-24","status":"new","parent_id":29,"id":34,"assignee":"Bartłomiej Nowak"},{"name":"Algorytmy sortujące","start_time":"2019-05-01","end_time":"2019-05-06","status":"pending","parent_id":null,"id":10,"assignee":"Jan Kowalski"}];
array=array.sort(function(a,b){ return a['id'] > b['id'] ? 1 : -1; });
console.log(array);
var new_array=[];
function display_date(){
    var i=0;
    var j=1;
    do{
        document.getElementById('date').innerHTML+='<td>2019-05-'+j+'</td>';
        i++;
        j++;
    }while(i<31);
}
var start_month=1;
var end_month=31;
var one_day_width=61;
var status_color={
    'pending':' #FF8C00',
    'new':' #FFFF00',
    'completed':'#00FF11'
};
var style_child_task={
    'height':'120px',
    'position':'absolute',
    'paddingTop':'1px',
    'border':'1px solid black'
};

var style_main_task={
    'position':'absolute',
    'height':'400px',
    'border':'1px solid black',
    'backgroundColor':'#A8A8A8'
}

var style_para_main={
    'height':'120px',
    'backgroundColor':'lightskyblue',
    'border':'1px solid black'
}

function set_styles(styles, element){
    for(var style in styles){
        let style_value=styles[style];
        element.style[style]=style_value;
    }
}
function count_day_spacing(i){
    var temp=array[i]['start_time'];
    var start=temp.charAt(temp.length-2)+temp.charAt(temp.length-1);
    var time= start-start_month;
    var spacing=one_day_width*time;
    return spacing-2;
}
function count_width(i){
    var temp=array[i]['start_time'];
    var start=temp.charAt(temp.length-2)+temp.charAt(temp.length-1);
    temp=array[i]['end_time'];
    var end=temp.charAt(temp.length-2)+temp.charAt(temp.length-1);
    start=parseInt(start);
    end=parseInt(end);
    var time= end-start;
    var days=(one_day_width*time)+one_day_width;
    return days;
}

function set_color(i){
    var temp=document.getElementById(array[i]['id'])
    temp.style.backgroundColor=status_color[array[i]['status']]||'#FFFFE0';
}

function create_paragraph(i){
    var para = document.createElement("p");
    var text_child=document.createTextNode(array[i]['name']);
    var temp_id= document.getElementById(array[i]['id']);
    para.appendChild(text_child);
    temp_id.appendChild(para);
    para = document.createElement("p");
    text_child=document.createTextNode(array[i]['assignee']);
    para.appendChild(text_child);
    temp_id.appendChild(para);

}
function kid_task_spacing(i,id){
    var space_minus=document.getElementById(id).offsetLeft;
    return count_day_spacing(i)-space_minus;
}

function display_kid_task(){
    var i=0
    var max=array.length;
    do{
        if(array[i]['parent_id']==null || array[i]['parent_id']==""){}
        else{
            var id=array[i]['parent_id'];
                if(document.getElementById(id)!=null){
                    var temp_create=document.getElementById(id);
                    var temp_div_create=document.createElement("div");
                    temp_div_create.id=array[i]['id'];
                    temp_div_create.setAttribute('class','task');
                    temp_div_create.style.marginLeft=kid_task_spacing(i,id)+'px';
                    temp_div_create.style.width=count_width(i)+'px';
                    set_styles(style_child_task,temp_div_create);
                    temp_create.appendChild(temp_div_create);
                    create_paragraph(i)
                    set_color(i);
                }
        }
        i++;
    }while(i<max);
}

function fix_positions(){
    var parent_id=document.getElementById('10').clientHeight;
    var top= parent_id;
    document.getElementById('29').style.top=top+'px';
    document.getElementById('29').style.height='650px';
    document.getElementById("34").style.height="370px"
}
function width_of_main_task(i){
    return count_width(i)-2;
}

function create_paragraph_main_task(i){
    var child_id=document.getElementById(array[i]['id']);
    var para=document.createElement("div");
    para.style.width=width_of_main_task(i)+'px';
    set_styles(style_para_main,para);
    var text_node=document.createTextNode(array[i]['name']+"<br>");
    var text_node2=document.createTextNode(array[i]['assignee']);
    para.appendChild(text_node);
    para.appendChild(text_node2);
    child_id.appendChild(para);
}

function display_main_task(){
    var i=0, j=0;
    var max=array.length;
    do{
        if(array[i]['parent_id']==null || array[i]['parent_id']==""){
            j++;
            var output_id=document.getElementById("main_output");
            var create_main_task=document.createElement("div");
            create_main_task.id=array[i]['id'];
            create_main_task.style.marginLeft=count_day_spacing(i)+'px';
            create_main_task.style.zIndex=j;
            set_styles(style_main_task,create_main_task);
            output_id.appendChild(create_main_task);
            create_paragraph_main_task(i);
        }
        i++;
    }while(i<max);
    display_kid_task();
}