A link anchor of a link is a point on the reference link that this link wants to reach as its endpoint. Link anchors are set via a linkAnchor property provided within link end definitions (i.e. the objects provided to link.source() and link.target() functions). (If the reference object is an Element, JointJS looks at anchor property instead.)

There are several built-in linkAnchor functions in JointJS:

Example:

link.source(link2, {
    linkAnchor: {
        name: 'connectionRatio',
        args: {
            ratio: 0.25
        }
    }
});

The default link anchor function is 'connectionRatio'; this can be changed with the defaultLinkAnchor paper option. Example:

paper.options.defaultLinkAnchor = {
    name: 'connectionLength',
    args: {
        length: 20
    }
};

JointJS also contains mechanisms to define one's own custom link anchor functions.