Getting the Link Object/Id

To work with links in the Gantt chart, you need to know how to get the object or id of a link. First of all, most methods take the link's object(id) as a parameter. Secondly, custom scenarios for links can't be implemented without referring to the link's object(id).

Getting the link object

To get a link object, use the getLink method:

gantt.getLink("link1");                //-> {id:"link1", source:1, target:2, type:1}

Getting all links from the Gantt chart

To get all links presented in the chart, use the getLinks method as in:

var links = gantt.getLinks();

It will return an array of links' objects.

Getting the links related to a certain task

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

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

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

The task.$source and task.$target are dynamic properties of the task object and contain ids of links connected to the task. The properties are not stored in the database but added to the task object dynamically after the data are loaded.

const task = gantt.getTask(1);
const source = task.$source;
// links that come from the task,
// `task #1` is a predecessor in these relations
 
source.forEach(function(linkId) {
   const link = gantt.getLink(linkId);
   console.log(link);
   // { id: linkId, source: 1, target: targetTaskId, ...}
});
 
const target = task.$target;
// links that come into the task,
// `task #1` is a successor in these relations
 
target.forEach(function(linkId) {
   const link = gantt.getLink(linkId);
   console.log(link);
   // { id: linkId, source: sourceTaskId, target: 1, ...}
});

Getting the link id

Generally, you can get the id of a link from the links object of the data set.

{
    tasks:[...],
    links:[
        { id:1, source:1, target:2, type:"1"},                       //link's id = 1         { id:2, source:2, target:3, type:"0"},                       //link's id = 2         { id:3, source:3, target:4, type:"0"}                        //link's id = 3     ]
}

If you want to get the id of link(s) with a specific "target", "source" or "type" value, use the technique as in:

//searching for a link that goes from the task with id=1 to the task with id=2
var links = gantt.serialize().links;                             //returns all links
for(var i=0;i<links.length; i++){                              //goes over all links
   if ( (links[i].source == 1) && (links[i].target == 2) )
       var linkId = links[i].id;
};

Changing the link id

To change the current id of a link, use the changeLinkId method:

gantt.changeLinkId(1274, "link14");          //changes the link id: 1274 -> "link14"