# Task Object/Id

To work with data in the Gantt chart, you need to know how to get the object or id of a data item. Firstly, most methods take the data object/id as a parameter. 
Secondly, any data-related code scenario can't be implemented without referring to the data object/id.

*To learn about available tree-related methods for tasks, refer to the [Task Parent/Child](guides/task-tree-operations.md) article.*

## Task object

To get a task object, use the [getTask](api/method/gettask.md) method:

~~~js
gantt.getTask("t1");
//->{id:"t1", text:"Task #5", start_date:"02-09-2020", duration:28, 
// progress:0.6, parent:"pr_2", $source:[3,5], $target:[2,1], ...}
~~~

## Parent of a task

To get the parent of a task, use the [getParent](api/method/getparent.md) method or the **parent** property of the task's object:

~~~js
gantt.getParent("t1"); //->"pr_2".If there is no parent, the method returns the root id
//or
var taskObj = gantt.getTask("t1"); //-> {id:"t1", text:"Task #5", parent:"pr_2", ...}
var taskParent = taskObj.parent;  //-> "pr_2"
~~~

*To see all methods related to the tree nature of the Gantt chart, read the [Task Parent/Child](guides/task-tree-operations.md) article.*

## Links connected to a task

For details about how to get all links connected to a specific task, see the [Getting the Link Object/Id](guides/link-object-operations.md#getting-the-links-related-to-a-certain-task) article.


## Task duration

To get the duration of a task, use the [calculateDuration](api/method/calculateduration.md) method:

~~~js
gantt.calculateDuration(new Date(2020,03,30),new Date (2020,04,02)); // ->16
~~~

The method won't work after only changing the **duration** parameter and updating the task object. To make it work, you also need to update the **end_date** parameter via the [calculateEndDate](api/method/calculateenddate.md) method. [Check the example](https://snippet.dhtmlx.com/f6keqhy5).

Note, if the [work_time](api/config/work_time.md) option is enabled, the [calculateDuration](api/method/calculateduration.md) method calculates the task's duration in working time. 

## Task height

To get the height of the DOM element of the task, use the [getTaskBarHeight](api/method/gettaskbarheight.md) method:

~~~js
gantt.config.bar_height = 45;
gantt.render();
 
gantt.getTaskBarHeight(1); // -> 45
~~~

The return value can also match the value specified to the **bar_height** property of the task object:

~~~js
var tasks = {
      data:[
         { id: 1, text: "Project #2", start_date: "01-04-2018", duration: 18, 
             progress: 0.4, open: true, bar_height: "full", row:height: 50 }, 
        { id: 2, text: "Task #1", start_date: "02-04-2018", duration: 8, 
            progress: 0.6, parent: 1, bar_height: 25, row:height: 50 },
       ]
};
gantt.init("gantt_here");
gantt.parse(tasks);

gantt.getTaskBarHeight(1); // -> 45
gantt.getTaskBarHeight(2); // -> 25
~~~

Note, if the **bar_height** property is specified to "full", the method calculates the height of the task bar in pixels.

## Task end date

To get the end date of a task, use the [calculateEndDate](api/method/calculateenddate.md) method:

~~~js
gantt.calculateEndDate(new Date(2020,03,30),48,"hour"); //-> Thu May 07 2020 17:00:00
~~~

Note, if the [work_time](api/config/work_time.md) option is enabled, the method considers duration as a working time. 


## Selected task

To get the currently selected task, use the [getSelectedId](api/method/getselectedid.md) method: 

~~~js
gantt.selectTask("t_1"); 
gantt.getSelectedId();  //-> "t_1" - the id of the selected task
~~~

## Tasks from a specific period

To get a collection of tasks that occur during the specified period, use the [getTaskByTime](api/method/gettaskbytime.md) method:

~~~js
var tasks = gantt.getTaskByTime(new Date(2020,03,05),new Date(2020,03,15)); 
// where tasks is an array of tasks' objects
~~~

## All tasks of Gantt 

To get all tasks presented in the Gantt chart, use the [getTaskByTime](api/method/gettaskbytime.md) method as in:

~~~js
var tasks = gantt.getTaskByTime();  //returns all tasks as an array of objects
~~~

You can also call the [serialize](api/method/serialize.md) method.


## Links of a certain task

To get links related to a task, use the **$source**, **$target** properties of the task object. The properties are autogenerated and store ids of the related links:

- **$source** - links that comes out from the task.
- **$target** - links that comes into task.

~~~js
var taskObj = gantt.getTask("t1");

var sourceLinks = taskObj.$source;  //-> ["l1","l4"] - ids of coming-out links  /*!*/
var targetLinks = taskObj.$target;  //-> ["l5","l8"] - ids of coming-into links  /*!*/
~~~


## Nearest oncoming task

To get the nearest oncoming task, use the [getTaskByTime](api/method/gettaskbytime.md) method as in:

~~~js
var tasks = gantt.getTaskByTime(new Date(), new Date(9999,1,1);    
// tasks - the list of all oncoming tasks
tasks.sort(function(a,b){ return (a.start_date > b.start_date ? 1 : -1); });
// tasks[0] - the nearest oncoming event
~~~

## Task id

Generally, you can get the id of a task from the "data" object of the data set. 

~~~js
{
    tasks:[
        {id:1, text:"Task #1", start_date:"01-04-2020", duration:18, progress:0.4}, /*!*/
        {id:2, text:"Task #2", start_date:"02-04-2020", duration:8,  progress:0.6}  /*!*/
    ],
    links:[...]
}
~~~

If you can't get the task's id from the data set, use the [getTaskByTime](api/method/gettaskbytime.md) method as in:

~~~js
var tasks = gantt.getTaskByTime();   //returns all tasks
for(var i="0;i" < tasks.length; i++){  //goes over all tasks to find the one needed
    if (tasks[i].text == "Task #3") 
        var taskId = tasks[i].id;
};
~~~

*If you know an approximate time when the needed task occurs, you'd better limit the returned collection of tasks in order to increase the app speed:*

~~~js
var tasks = gantt.getTaskByTime(new Date(2020,05,01),new Date(2020,05,10)); 
for(var i="0;i" < tasks.length; i++){  
    if (tasks[i].text == "Task #3") 
        var taskId = tasks[i].id;
};
~~~

### Changing id of a task

To change the current id of a task, use the [changeTaskId](api/method/changetaskid.md) method:

~~~js
gantt.changeTaskId("t1", "t11");  //changes the task id from "t1" to "t11" 
~~~


## Opening/Closing task branches

The open state of a task branch is defined by the **task.$open** property, which is available after tasks are loaded into gantt.
Once the value is modified, the changes will be displayed after the next repainting of the gantt:

~~~js
// expand all branches
gantt.eachTask(function(task){
    task.$open = true;
});
gantt.render();

// collapse all branches
gantt.eachTask(function(task){
    task.$open = false;
});
gantt.render();
~~~

In order to open/close a single task, you can use the [open](api/method/open.md) and [close](api/method/close.md) methods. They'll change the inner state of the task and invoke repainting. 
However, to modify many tasks, it's better to work with **task.$open** directly in order to avoid unnecessary repaintings.

## Copying/pasting tasks

Follow the examples given in the [How to copy and paste tasks](guides/how-to.md#how-to-copy-and-paste-tasks) section.