TypeScript Lab: Load Styles Dynamically

LAB / EXPLORATION

TypeScript Lab: Load Styles Dynamically

Planned

LAB 070 — DOM & Async
Insert a stylesheet link and show the resulting style change.

LAB TypeScript Lab: Load Styles Dynamically Preview coming soon

LAB 070

TypeScript Lab: Load Styles Dynamically

Concept

Promises can resolve when dynamically created external resources finish loading.

Concept

Promises can resolve when dynamically created external resources finish loading.

Objective & Explanation

What the project should make visible and why the concept matters.

Learning Target

Objective

Insert a stylesheet link and show the resulting style change.

Explanation

Promises can resolve when dynamically created external resources finish loading.

Project Plan

Structure, technologies, data boundary, and source connection.

Structure

project/
├── package.json
├── tsconfig.json
├── index.html
├── styles.css
└── src/
    └── app.ts

Technologies

TypeScript
DOM
HTML
CSS

Data Layer

No persistent data layer. Keep all demonstration values inside the standalone project.

Sandbox Source

src/local-editor/client.ts → loadStyle()

Build Instructions

Build only the focused behavior, then use the visual layer to inspect it.

Setup

Create the standalone project folder and listed files.

Implement

Implement the smallest version that demonstrates the concept.

Run & Inspect

Change one input and observe the visible output change.

Code & Configuration

Starter configuration plus the focused implementation example.

Focused TypeScript

Implement this behavior first, then alter the input.

function loadStyle(url: string): Promise<void> {
  return new Promise((resolve, reject) => {
    const link = document.createElement("link");
    link.rel = "stylesheet";
    link.href = url;
    link.onload = () => resolve();
    link.onerror = () => reject(new Error("Style failed"));
    document.head.append(link);
  });
}

Starter Configuration

Keep the project independently buildable.

package.json

{
  "type": "module",
  "scripts": { "build": "tsc" },
  "devDependencies": { "typescript": "^7.0.2" }
}

tsconfig.json

{
  "compilerOptions": {
    "rootDir": "./src",
    "outDir": "./dist",
    "target": "ES2022",
    "module": "ES2022",
    "lib": ["ES2022", "DOM"],
    "strict": true,
    "sourceMap": true
  },
  "include": ["src/**/*.ts"]
}

Expected Visual Result

The output is the proof that the concept is working.

Visible Proof

The browser should visibly demonstrate: insert a stylesheet link and show the resulting style change.

Data: None