A: basic concepts
BOM: refers to the browser model enables JS able to communicate with the browser
DOM: refers to the HTML document object model can access all document elements through it
Two: window window
(1) All browsers support the window object. It represents the browser window.
(2) * If the document contains a frame (frame or iframe tag), the browser will create a window object as an HTML document, and create an additional window object for each frame.
(3) * does not apply to public standard window object, but all browsers support the object.
(4) All JavaScript global objects, functions, and variables are automatically members of the window object.
(5) is a global variable property of the window object. Global function is the window object.
(6) The next talk about the HTML DOM document window is one of the attributes of the object.