📄 17-2.html
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<head><script>// This function is passed a DOM Node object and checks to see if that node // represents a string of text: i.e., if the node is a Text object. If// so, it returns the length of the string. If not, it recursively// calls itself on each of the children of the node and adds up the// total length of the text it finds. Note that it enumerates the// children of a node using the firstChild and nextSibling properties.// Note that the function does not recurse when it finds a Text node// because Text nodes never have children.function countCharacters(n) { // n is a Node if (n.nodeType == 3 /*Node.TEXT_NODE*/) // Check if n is a Text object return n.length; // If so, return its length. // Otherwise, n may have children whose characters we need to count var numchars = 0; // Used to hold total characters of the children // Instead of using the childNodes property, this loop examines the // children of n using the firstChild and nextSibling properties. for(var m = n.firstChild; m != null; m = m.nextSibling) { numchars += countCharacters(m); // Add up total characters found } return numchars; // Return total characters}</script></head><!-- The onload event handler is an example of how the countCharacters() function might be used. Note that we only want to count the characters in the <body> of the document, so we pass document.body to the function.--><body onload="alert('Document length: ' + countCharacters(document.body))">This is a sample document.<p>How long is it?</body>⌨️ 快捷键说明
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