通过移除空行和注释来压缩 javascript 代码
我要评论
/**
* 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();
}
}
}
总结
以上就是本文关于通过java压缩javascript代码实例分享的全部内容，希望对大家有所帮助。感兴趣的朋友可以继续参阅本站其他相关专题，如有不足之处，欢迎留言指出。感谢朋友们对本站的支持！
如对本文有疑问， 点击进行留言回复！！
idea ssm项目java程序向串口发送指令并且使用十六进制 rxtx包的方法
网友评论