通过移除空行和注释来压缩 JavaScript 代码

/** * This file is part of the Echo Web Application Framework (hereinafter \"Echo\"). * Copyright (C) 2002-2009 NextApp, Inc. * * Compresses a String containing JavaScript by removing comments and whitespace. */public class JavaScriptCompressor { private static final char LINE_FEED = \'\\n\'; private static final char CARRIAGE_RETURN = \'\\r\'; private static final char SPACE = \' \'; private static final char TAB = \'\\t\'; /** * Compresses a String containing JavaScript by removing comments and * whitespace. * * @param script the String to compress * @return a compressed version */ public static String compress(String script) { JavaScriptCompressor jsc = new JavaScriptCompressor(script); return jsc.outputBuffer.toString(); } /** Original JavaScript text. */ private String script; /** * Compressed output buffer. * This buffer may only be modified by invoking the <code>append()</code> * method. */ private StringBuffer outputBuffer; /** Current parser cursor position in original text. */ private int pos; /** Character at parser cursor position. */ private char ch; /** Last character appended to buffer. */ private char lastAppend; /** Flag indicating if end-of-buffer has been reached. */ private Boolean endReached; /** Flag indicating whether content has been appended after last identifier. */ private Boolean contentAppendedAfterLastIdentifier = true; /** * Creates a new <code>JavaScriptCompressor</code> instance. * * @param script */ private JavaScriptCompressor(String script) { this.script = script; outputBuffer = new StringBuffer(script.length()); nextchar(); while (!endReached) { if (Character.isJavaIdentifierStart(ch)) { renderIdentifier(); } else if (ch == \' \') { skipWhiteSpace(); } else if (isWhitespace()) { // Compress whitespace skipWhiteSpace(); } else if ((ch == \'\"\') || (ch == \'\\\'\')) { // Handle strings renderString(); } else if (ch == \'/\') { // Handle comments nextChar(); if (ch == \'/\') { nextChar(); skipLineComment(); } else if (ch == \'*\') { nextChar(); skipBlockComment(); } else { append(\'/\'); } } else { append(ch); nextChar(); } } } /** * Append character to output. * * @param ch the character to append */ private void append(char ch) { lastAppend = ch; outputBuffer.append(ch); contentAppendedAfterLastIdentifier = true; } /** * Determines if current character is whitespace. * * @return true if the character is whitespace */ private boolean isWhitespace() { return ch == CARRIAGE_RETURN || ch == SPACE || ch == TAB || ch == LINE_FEED; } /** * Load next character. */ private void nextChar() { if (!endReached) { if (pos < script.length()) { ch = script.charAt(pos++); } else { endReached = true; ch = 0; } } } /** * Adds an identifier to output. */ private void renderIdentifier() { if (!contentAppendedAfterLastIdentifier) append(SPACE); append(ch); nextChar(); while (Character.isJavaIdentifierPart(ch)) { append(ch); nextChar(); } contentAppendedAfterLastIdentifier = false; } /** * Adds quoted String starting at current character to output. */ private void renderString() { char startCh = ch; // Save quote char append(ch); nextChar(); while (true) { if ((ch == LINE_FEED) || (ch == CARRIAGE_RETURN) || (endReached)) { // JavaScript error: string not terminated return; } else { if (ch == \'\\\\\') { append(ch); nextChar(); if ((ch == LINE_FEED) || (ch == CARRIAGE_RETURN) || (endReached)) { // JavaScript error: string not terminated return; } append(ch); nextChar(); } else { append(ch); if (ch == startCh) { nextChar(); return; } nextChar(); } } } } /** * Moves cursor past a line comment. */ private void skipLineComment() { while ((ch != CARRIAGE_RETURN) && (ch != LINE_FEED)) { if (endReached) { return; } nextChar(); } } /** * Moves cursor past a block comment. */ private void skipBlockComment() { while (true) { if (endReached) { return; } if (ch == \'*\') { nextChar(); if (ch == \'/\') { nextChar(); return; } } else nextChar(); } } /** * Renders a new line character, provided previously rendered character * is not a newline. */ private void renderNewLine() { if (lastAppend != \'\\n\' && lastAppend != \'\\r\') { append(\'\\n\'); } } /** * Moves cursor past white space (including newlines). */ private void skipWhiteSpace() { if (ch == LINE_FEED || ch == CARRIAGE_RETURN) { renderNewLine(); } else { append(ch); } nextChar(); while (ch == LINE_FEED || ch == CARRIAGE_RETURN || ch == SPACE || ch == TAB) { if (ch == LINE_FEED || ch == CARRIAGE_RETURN) { renderNewLine(); } nextChar(); } }}

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