Document. compatMode Introduction

The document. compatMode is very helpful for developing compatible web pages. We all know that the rendering of the box model by IE is very different in Standards Mode and Quirks Mode, the interpretation of the Box Model in Standards Mode is the same as that in other standard browsers, but there is a big difference in Quirks Mode, without declaring Doctype, by default, IE is in Quirks Mode. Therefore, for compatibility consideration, we may need to obtain the current document rendering method.
Document. compatMode comes in handy. It has two possible return values: BackCompat and CSS1Compat, which are explained as follows:
BackCompat Standards-compliant mode is not switched on. (Quirks Mode)
CSS1Compat Standards-compliant mode is switched on. (Standards Mode)
In the actual project, we also need to obtain whether the browser is IE, so that we can get the IE rendering mode. Code in Ext: isBorderBox = isIE &&! IsStrict.
When the document has a standard declaration, the value of document. compatMode is equal to "CSS1compat". Therefore, we can judge whether the document has a standard declaration based on the value of document. compatMode.
Var height = document. compatMode = "CSS1Compat "? Document.doc umentElement. clientHeight: document. body. clientHeight;