📄 17-1.html
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<head><script>// This function is passed a DOM Node object and checks to see if that node // represents an HTML tag: i.e., if the node is an Element object. It// recursively calls itself on each of the children of the node, testing// them in the same way. It returns the total number of Element objects// it encounters. If you invoke this function by passing it the// Document object, it traverses the entire DOM tree.function countTags(n) { // n is a Node var numtags = 0; // Initialize the tag counter if (n.nodeType == 1 /*Node.ELEMENT_NODE*/) // Check if n is an Element numtags++; // Increment the counter if so var children = n.childNodes; // Now get all children of n for(var i=0; i < children.length; i++) { // Loop through the children numtags += countTags(children[i]); // Recurse on each one } return numtags; // Return total number of tags}</script></head><!-- Here's an example of how the countTags() function might be used --><body onload="alert('This document has ' + countTags(document) + ' tags')">This is a <i>sample</i> document.</body>⌨️ 快捷键说明
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