One item per line (row) in timeline? - Vis.js - vis.js

Question

Is there a way to always have one item per line in the timeline? I don't want two or more items to share the same line, whatever the dates are.
Thanks.

Answer 1

You have to use groups, or if you're already using those for another purpose, you have to use subgroups.
Here's the official documentation for items, groups and subgroups (I'm assuming the website isn't gonna expire anytime soon... again...).
If you can use groups
Specify a different group for every item. You can set the group's content as an empty string, if you don't want to have a label for it on the left side of the Timeline.
If you want to arrange the groups in a specific way, specify an ordering function as the Timeline's options' groupOrder property. Example:
var options = {
// other properties...
groupOrder: function (a, b) {
if(a.content > b.content)// alphabetic order
return 1;
else if(a.content < b.content)
return -1;
return 0;
}
};
If you have to use subgroups
When you create an item, put it in the group it belongs to but also specify for it the subgroup property so that it's unique, like the item's id. For example, you can use the id itself, or add a prefix or suffix to it.
In the Timeline's options, set the stack and stackSubgroups properties to true.
In each group, set the subgroupStack property to true and specify an ordering function as the group's subgroupOrder property. Example:
var group = {
id: 1,
content: 'example group',
subgroupStack: true,
subgroupOrder: function(a, b) {
var tmp = a.start.getTime() - b.start.getTime();
return tmp === 0 ? parseInt(a.id) - parseInt(b.id) : tmp;
// if the start dates are the same, I compare the items' ids.
// this is because due to a bug (I guess) the ordering of items
// that return 0 in the ordering function might "flicker" in certain
// situations. if you want to order the items alphabetically in that
// case, compare their "content" property, or whatever other
// property you want.
}
};