Created
May 20, 2017 21:06
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Palindrome Highlighter
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| <!DOCTYPE html> | |
| <html> | |
| <head> | |
| <meta charset="UTF-8" /> | |
| <meta name="author" content="Yi-Fan Zhang" /> | |
| <title>Palindromes</title> | |
| <style> | |
| .editor { | |
| position: relative; | |
| } | |
| .editor textarea { | |
| resize: none; | |
| font-family: inherit; | |
| font-size: inherit; | |
| } | |
| .editor .editor-common { | |
| position: absolute; | |
| top: 0; | |
| left: 0; | |
| background-color: transparent; | |
| margin: 0; | |
| padding: 0; | |
| height: 150px; | |
| width: 500px; | |
| overflow: hidden; | |
| white-space: pre-wrap; | |
| word-wrap: break-word; | |
| } | |
| .editor .editor-front { | |
| background-color: transparent; | |
| } | |
| .editor .editor-back { | |
| border: 1px solid grey; | |
| color: transparent; | |
| } | |
| .highlight { | |
| background-color: yellow; | |
| } | |
| </style> | |
| </head> | |
| <body> | |
| <div class="editor"> | |
| <div id="editor-textarea-back" class="editor-back editor-common"></div> | |
| <textarea id="editor-textarea" class="editor-front editor-common">Here are some palindromes: racecar, deed and eye. If you can think of some more, type them in here.</textarea> | |
| </div> | |
| </body> | |
| <script type="text/javascript"> | |
| (function() { | |
| var textarea = document.getElementById("editor-textarea"); | |
| var textarea_back = document.getElementById("editor-textarea-back"); | |
| var timer; | |
| update(); | |
| textarea.addEventListener("keydown", update); | |
| function update() { | |
| textarea_back.innerHTML = ""; | |
| if (timer) clearTimeout(timer); | |
| timer = setTimeout(function() { | |
| textarea_back.innerHTML = highlight_palindrome(textarea.value); | |
| textarea_back.scrollTop = textarea.scrollTop; | |
| }, 500); | |
| } | |
| function highlight_palindrome(str) { | |
| var lines = str.split(/\n/); | |
| var i, j, words, word, match, new_words, new_lines = []; | |
| for (i = 0; i < lines.length; i++) { | |
| words = lines[i].split(/\s/); | |
| new_words = []; | |
| for (j = 0; j < words.length; j++) { | |
| word = words[j]; | |
| match = word.match(/([A-Za-z]+)/); | |
| if (match && match[0].length > 2 | |
| && is_palindrome(match[0].toLowerCase())) { | |
| word = word.slice(0, match.index) | |
| + '<span class="highlight">' | |
| + word.substring(match.index, match[0].length) | |
| + '</span>' | |
| + word.substring(match.index + match[0].length); | |
| } | |
| new_words.push(word); | |
| } | |
| new_lines.push(new_words.join(' ').replace(/\n/g,'<br/>')); | |
| } | |
| return new_lines.join('<br/>') + '<br/>'; | |
| } | |
| function is_palindrome(word) { | |
| if (word.length < 2) { | |
| return true; | |
| } else if (word[0] === word[word.length - 1]) { | |
| return is_palindrome(word.slice(1,-1)); | |
| } else { | |
| return false; | |
| } | |
| } | |
| })(); | |
| </script> | |
| </html> |
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