> For the complete documentation index, see [llms.txt](https://raozhanping.gitbook.io/notes/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://raozhanping.gitbook.io/notes/node/node-chai.md).

# chai.js 断言库

> BDD风格的expect/should API，\
> TDD 风格的Assert API

## BDD

expect 和 should 是 BDD 风格的，二者使用相同的链式语言来组织断言，但不同于他们初始化断言的方式：expect 使用构造函数来创建断言对象实例，而should通过为Object.protorype新增方法来实现断言（所以should 不支持 IE）；expect 直接指向 chai.expect ,而 should 则是chai.should().

## 语言链

* to
* be
* been
* is
* that
* which
* and
* has
* have
* with
* at
* of
* same

## .not

对之后的断言取反

```javascript
expect(foo).to.not.equal('bar');
expect(goodFn).to.not.throw(Error);
expect({ foo: 'baz' }).to.have.property('foo').and.not.equal('bar');
```

## .deep