I have an array of objects that determine which ones should be showed first. An example of this array would be:
[
{
"id": "b94ae1a5-c6b2-4e45-87cd-a4036fdb7870",
"prerequisites_ids": [
"2a4fdd9c-45d0-49d9-a0eb-ba5a0464f2b1"
]
},
{
"id": "ef7d2415-808f-4efc-939e-2692f38a5ee7",
"prerequisites_ids": [
"74e41a2c-e74e-4016-bb2c-f2e84c04fe92"
]
},
{
"id": "74e41a2c-e74e-4016-bb2c-f2e84c04fe92",
"prerequisites_ids": []
},
{
"id": "2a4fdd9c-45d0-49d9-a0eb-ba5a0464f2b1",
"prerequisites_ids": [
"ef7d2415-808f-4efc-939e-2692f38a5ee7"
]
}
]
How could I sort it to get this?
[
{
"id": "74e41a2c-e74e-4016-bb2c-f2e84c04fe92",
"prerequisites_ids": []
},
{
"id": "ef7d2415-808f-4efc-939e-2692f38a5ee7",
"prerequisites_ids": [
"74e41a2c-e74e-4016-bb2c-f2e84c04fe92"
]
},
{
"id": "2a4fdd9c-45d0-49d9-a0eb-ba5a0464f2b1",
"prerequisites_ids": [
"ef7d2415-808f-4efc-939e-2692f38a5ee7"
]
},
{
"id": "b94ae1a5-c6b2-4e45-87cd-a4036fdb7870",
"prerequisites_ids": [
"2a4fdd9c-45d0-49d9-a0eb-ba5a0464f2b1"
]
}
]
I have tried creating a custom function:
export function comparePrerequisites(a, b) {
if (!a.prerequisites_ids) {
return -1
}
if (a.prerequisites_ids.includes(b.id)) {
return 1;
}
}
data.sort(comparePrerequisites)
but does not seem to work. Thanks in advance!
We have here the requirements for a topological sort. This is not a job for the sort method. Instead you can use recursion (a DFS traversal) to drill down to a dependency that is already collected, or to a leaf (no dependencies).
Here is an implementation:
function topologicalSort(tasks) {
const visited = new Set;
const taskMap = new Map(tasks.map(task => [task.id, task]));
function dfs(tasks) {
for (let task of tasks) {
if (!visited.has(task.id)) {
dfs(task.prerequisites_ids.map(id => taskMap.get(id)));
}
visited.add(task);
}
}
dfs(tasks);
return [...visited];
}
// Demo on your example:
let tasks = [{"id": "b94ae1a5-c6b2-4e45-87cd-a4036fdb7870","prerequisites_ids": ["2a4fdd9c-45d0-49d9-a0eb-ba5a0464f2b1"]},{"id": "ef7d2415-808f-4efc-939e-2692f38a5ee7","prerequisites_ids": ["74e41a2c-e74e-4016-bb2c-f2e84c04fe92"]},{"id": "74e41a2c-e74e-4016-bb2c-f2e84c04fe92","prerequisites_ids": []},{"id": "2a4fdd9c-45d0-49d9-a0eb-ba5a0464f2b1","prerequisites_ids": ["ef7d2415-808f-4efc-939e-2692f38a5ee7"]}];
console.log(topologicalSort(tasks));