TypeScript error–Property ‘assign’ does not exists on type ‘ObjectConstructor’

A colleague asked me for help when he got into trouble with his TypeScript code. Here is a simplified version:

	var obj = { a: 1 };
	var copy = Object.assign({}, obj);
	console.log(copy); // { a: 1 }

view raw assigntest.ts hosted with ❤ by GitHub

Although this looks like valid code, the TypeScript compiler complained:

After some headscratching, we discovered that there was a “rogue” tsconfig.json at a higher level that set “ES5” as the target. Object.Assign was added as part of “ES6” explaining why TypeScript complained.

After changing the target to “es6”, the error disappeared.