Javascript learning 6-javascript object-oriented (practice) production and debugging logs

Generally, when javascript looks at the effect, alert functions are often used. Imagine if we want to see how many objects there are under the document, we may write the code like this: [javascript] for (iindocument ){... syntaxHighlighter. all (); generally, when javascript looks at the effect, alert functions are often used. Imagine if we want to see how many objects there are under the document, then we may write this code: [javascript] for (I in document) {alert (I);} but there are more than one hundred objects in the document, so we need to click more than one hundred times in the browser to see the whole. Therefore, we will make a simple log debugging, which is also a consolidation of our previous learning knowledge. The Calling page is as follows: [html] Untitled document