structural-typing

TypeScript uses structural typing: if it has the right shape, it fits.

Unlike nominal typing (where types must be explicitly declared), TypeScript checks structure. Understanding this prevents surprises and unlocks powerful patterns.

If you're surprised that TypeScript accepts a value, you're probably assuming nominal typing.

当对 TypeScript 接受意外值感到惊讶时使用。设计函数参数时使用。使用模拟对象进行测试时使用。 来源：marius-townhouse/effective-typescript-skills。