Project references
- TypeScript course
- Expert
- Lesson 14/35
- 4 min
Learn multi-project setups with project references.
What are project references?
The references array lists the projects a project depends on; each entry points to a target tsconfig.json via a path field. This is used to split projects in a monorepo. Referenced projects must have composite: true.
{
"references": [
{ "path": "../core" },
{ "path": "../utils" }
]
}Build mode compiles references automatically first.
The composite requirement
If a project is referenced it must have composite: true; otherwise tsc --build errors out. Composite also forces declaration: true and outDir so the referencing project can find type declarations.
// core/tsconfig.json
{
"compilerOptions": {
"composite": true,
"declaration": true,
"outDir": "dist"
}
}Referencing a non-composite project is a compile error.
Practice Resolve build order
Write a resolveBuildOrder function that returns the topological order based on each project's references. For dependencies app → core, core → utils, produce the output utils, core, app.
Starter code
// resolveBuildOrder: references'a göre topolojik sıra verir
// her projenin references'ını takip et
// bağımlılık sırasıyla listele
// sonucu join ile yazdırSample solution
function resolveBuildOrder(projects: { name: string; references: string[] }[]): string[] {
const order: string[] = [];
const visited = new Set<string>();
function visit(name: string) {
if (visited.has(name)) return;
visited.add(name);
const project = projects.find(p => p.name === name);
if (project) {
for (const ref of project.references) {
visit(ref);
}
}
order.push(name);
}
for (const p of projects) visit(p.name);
return order;
}
const projects = [
{ name: "app", references: ["core"] },
{ name: "core", references: ["utils"] },
{ name: "utils", references: [] }
];
console.log(resolveBuildOrder(projects).join(", "));Expected output
utils, core, app
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 What does each entry in the references array contain?
- A type field
- A path field Correct answer
- A name field
- A version field
Explanation: Each reference entry contains a path field pointing to the target tsconfig.json; name, version, and type are not part of the reference shape.
2 Add a reference path
{
"references": [
{ "____": "../core" }
]
}{
"references": [
{ "path": "../core" }
]
}Explanation: Each reference entry uses a path field to point to the target tsconfig.json; name, dir, and ref are not valid fields.
3 Project references parts
| Term | Meaning |
|---|---|
references |
lists dependent projects |
path |
points to the target tsconfig |
composite: true |
enables referenceability |
declaration: true |
produces type declarations |