isLinkAllowed

checks whether the specified link is correct

linkOrFrom	string | number | LinkForValidation	either ID of the source (predecessor) task or a link object with the following properties:
from_start	boolean	optional, specifies if the link is being dragged from the start of the source (predecessor) task (*true*) or from its end (*false*). Not needed at all when the first parameter is specified as an object
to	string | number | null | undefined	optional, the ID of the target (successor) task. Can have the *null* or *undefined* value if the target task isn't specified yet. Not needed at all when the first parameter is specified as an object
to_start	boolean	optional, specifies if the link is being dragged to the start of the target (successor) task (*true*) or from its end (*false*). Not needed at all when the first parameter is specified as an object

boolean

true, if the link is correct. Otherwise, false

Example

const link = {
    source:2,
    target:2,
    type:gantt.config.link.start_to_start
};
if(gantt.isLinkAllowed(link))// -> false (because source==target)
    gantt.addLink(link);

The link object is different from the Link object and has only 3 properties:

• source - (string | number) - the ID of the source (predecessor) task.
• target - (string | number) - the ID of the target (successor) task.
• type - (string) - the link type.

The cases when a link is considered as incorrect:

1. The source task's id is equal to the target task's id.
2. If the type is set to a value that is not 0, 1, 2, or 3.
3. If the link failed the validation.
4. If the link is created from the project task to its sub-task. The dates of the project task depend on the dates of children tasks.

Note, there is the 2nd way to call the method:

gantt.isLinkAllowed(from, from_start, to, to_start )

Here is the type description of the arguments:

• from - (string | number | object) - either ID of the source (predecessor) task or a link object with the following properties:
• from_start? - (boolean) - optional, specifies if the link is being dragged from the start of the source (predecessor) task (true) or from its end (false). Not needed at all when the first parameter is specified as an object
• to? - (string | number | null | undefined *) - optional, the ID of the target (successor) task. Can have the *null or undefined value if the target task isn't specified yet. Not needed at all when the first parameter is specified as an object
• to_start? - (boolean) - optional, specifies if the link is being dragged to the start of the target (successor) task (true) or from its end (false). Not needed at all when the first parameter is specified as an object

For example, the code above you alter as in:

//var link = {
//    source:2,
//    target:2,
//    type:gantt.config.link.start_to_start
//};
 
if(gantt.isLinkAllowed(2, true, 2, true))// -> false (because source==target)
    //do something

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