利用Java来压缩 JavaScript 代码，javajavascript,通过移除空行和注释来压缩

利用Java来压缩 JavaScript 代码，javajavascript,通过移除空行和注释来压缩

通过移除空行和注释来压缩JavaScript代码```java/ * 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) &amp;&amp; (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\' &amp;&amp; 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();    }}

}```