Using Google Chrome extension APIs in TypeScript

As of TypeScript 2 (or 2.x, not sure), you should import the Google Chrome types from @types.

In package.json:

"devDependencies": {
    ...
    "@types/chrome": "0.0.35", // Or just npm install --save-dev @types/chrome

And in tsconfig:

    "types": [
        // (various types, e.g. jquery, core-js),
        "chrome"
    ]