function 里的 this 在不同的时候，会有不同的表现，一般会有以下四种情况
Invocation as a function
Invocation as a method
Invocation as a constructor
Invocatuon with the apply() and call() method继续阅读 »
Floats, absolutely positioned elements, block containers (such as inline-blocks, table-cells, and table-captions) that are not block boxes, and block boxes with 'overflow' other than 'visible' (except when that value has been propagated to the viewport) establish new block formatting contexts for their contents.继续阅读 »