Mega Code Archive
Escape and unescape javascript code
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/*
* Copyright 2005 Joe Walker
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import java.util.Arrays;
import java.util.Locale;
import java.util.SortedSet;
import java.util.TreeSet;
/**
* Various Javascript code utilities.
* The escape classes were taken from jakarta-commons-lang which in turn
* borrowed from Turbine and other projects. The list of authors below is almost
* certainly far too long, but I'm not sure who really wrote these methods.
* @author Joe Walker [joe at getahead dot ltd dot uk]
* @author Henri Yandell
* @author Alexander Day Chaffee
* @author Antony Riley
* @author Helge Tesgaard
* @author Sean Brown
* @author Gary Gregory
* @author Phil Steitz
* @author Pete Gieser
*/
public class JavascriptUtil
{
/**
* <p>Escapes the characters in a <code>String</code> using JavaScript String rules.</p>
* <p>Escapes any values it finds into their JavaScript String form.
* Deals correctly with quotes and control-chars (tab, backslash, cr, ff, etc.) </p>
*
* <p>So a tab becomes the characters <code>'\\'</code> and
* <code>'t'</code>.</p>
*
* <p>The only difference between Java strings and JavaScript strings
* is that in JavaScript, a single quote must be escaped.</p>
*
* <p>Example:
* <pre>
* input string: He didn't say, "Stop!"
* output string: He didn\'t say, \"Stop!\"
* </pre>
* </p>
*
* @param str String to escape values in, may be null
* @return String with escaped values, <code>null</code> if null string input
*/
public static String escapeJavaScript(String str)
{
if (str == null)
{
return null;
}
StringBuffer writer = new StringBuffer(str.length() * 2);
int sz = str.length();
for (int i = 0; i < sz; i++)
{
char ch = str.charAt(i);
// handle unicode
if (ch > 0xfff)
{
writer.append("\\u");
writer.append(hex(ch));
}
else if (ch > 0xff)
{
writer.append("\\u0");
writer.append(hex(ch));
}
else if (ch > 0x7f)
{
writer.append("\\u00");
writer.append(hex(ch));
}
else if (ch < 32)
{
switch (ch)
{
case '\b':
writer.append('\\');
writer.append('b');
break;
case '\n':
writer.append('\\');
writer.append('n');
break;
case '\t':
writer.append('\\');
writer.append('t');
break;
case '\f':
writer.append('\\');
writer.append('f');
break;
case '\r':
writer.append('\\');
writer.append('r');
break;
default:
if (ch > 0xf)
{
writer.append("\\u00");
writer.append(hex(ch));
}
else
{
writer.append("\\u000");
writer.append(hex(ch));
}
break;
}
}
else
{
switch (ch)
{
case '\'':
// If we wanted to escape for Java strings then we would
// not need this next line.
writer.append('\\');
writer.append('\'');
break;
case '"':
writer.append('\\');
writer.append('"');
break;
case '\\':
writer.append('\\');
writer.append('\\');
break;
default:
writer.append(ch);
break;
}
}
}
return writer.toString();
}
/**
* <p>Returns an upper case hexadecimal <code>String</code> for the given
* character.</p>
* @param ch The character to convert.
* @return An upper case hexadecimal <code>String</code>
*/
private static String hex(char ch)
{
return Integer.toHexString(ch).toUpperCase(Locale.ENGLISH);
}
/**
* <p>Unescapes any JavaScript literals found in the <code>String</code>.</p>
* <p>For example, it will turn a sequence of <code>'\'</code> and <code>'n'</code>
* into a newline character, unless the <code>'\'</code> is preceded by another
* <code>'\'</code>.</p>
* @param str the <code>String</code> to unescape, may be null
* @return A new unescaped <code>String</code>, <code>null</code> if null string input
*/
public static String unescapeJavaScript(String str)
{
if (str == null)
{
return null;
}
StringBuffer writer = new StringBuffer(str.length());
int sz = str.length();
StringBuffer unicode = new StringBuffer(4);
boolean hadSlash = false;
boolean inUnicode = false;
for (int i = 0; i < sz; i++)
{
char ch = str.charAt(i);
if (inUnicode)
{
// if in unicode, then we're reading unicode
// values in somehow
unicode.append(ch);
if (unicode.length() == 4)
{
// unicode now contains the four hex digits
// which represents our unicode character
try
{
int value = Integer.parseInt(unicode.toString(), 16);
writer.append((char) value);
unicode.setLength(0);
inUnicode = false;
hadSlash = false;
}
catch (NumberFormatException nfe)
{
throw new IllegalArgumentException("Unable to parse unicode value: " + unicode + " cause: " + nfe);
}
}
continue;
}
if (hadSlash)
{
// handle an escaped value
hadSlash = false;
switch (ch)
{
case '\\':
writer.append('\\');
break;
case '\'':
writer.append('\'');
break;
case '\"':
writer.append('"');
break;
case 'r':
writer.append('\r');
break;
case 'f':
writer.append('\f');
break;
case 't':
writer.append('\t');
break;
case 'n':
writer.append('\n');
break;
case 'b':
writer.append('\b');
break;
case 'u':
// uh-oh, we're in unicode country....
inUnicode = true;
break;
default:
writer.append(ch);
break;
}
continue;
}
else if (ch == '\\')
{
hadSlash = true;
continue;
}
writer.append(ch);
}
if (hadSlash)
{
// then we're in the weird case of a \ at the end of the
// string, let's output it anyway.
writer.append('\\');
}
return writer.toString();
}
/**
* Check to see if the given word is reserved or a bad idea in any known
* version of JavaScript.
* @param name The word to check
* @return false if the word is not reserved
*/
public static boolean isReservedWord(String name)
{
return reserved.contains(name);
}
/**
* The array of javascript reserved words
*/
private static final String[] RESERVED_ARRAY = new String[]
{
// Reserved and used at ECMAScript 4
"as",
"break",
"case",
"catch",
"class",
"const",
"continue",
"default",
"delete",
"do",
"else",
"export",
"extends",
"false",
"finally",
"for",
"function",
"if",
"import",
"in",
"instanceof",
"is",
"namespace",
"new",
"null",
"package",
"private",
"public",
"return",
"super",
"switch",
"this",
"throw",
"true",
"try",
"typeof",
"use",
"var",
"void",
"while",
"with",
// Reserved for future use at ECMAScript 4
"abstract",
"debugger",
"enum",
"goto",
"implements",
"interface",
"native",
"protected",
"synchronized",
"throws",
"transient",
"volatile",
// Reserved in ECMAScript 3, unreserved at 4 best to avoid anyway
"boolean",
"byte",
"char",
"double",
"final",
"float",
"int",
"long",
"short",
"static",
// I have seen the following list as 'best avoided for function names'
// but it seems way to all encompassing, so I'm not going to include it
/*
"alert", "anchor", "area", "arguments", "array", "assign", "blur",
"boolean", "button", "callee", "caller", "captureevents", "checkbox",
"clearinterval", "cleartimeout", "close", "closed", "confirm",
"constructor", "date", "defaultstatus", "document", "element", "escape",
"eval", "fileupload", "find", "focus", "form", "frame", "frames",
"getclass", "hidden", "history", "home", "image", "infinity",
"innerheight", "isfinite", "innerwidth", "isnan", "java", "javaarray",
"javaclass", "javaobject", "javapackage", "length", "link", "location",
"locationbar", "math", "menubar", "mimetype", "moveby", "moveto",
"name", "nan", "navigate", "navigator", "netscape", "number", "object",
"onblur", "onerror", "onfocus", "onload", "onunload", "open", "opener",
"option", "outerheight", "outerwidth", "packages", "pagexoffset",
"pageyoffset", "parent", "parsefloat", "parseint", "password",
"personalbar", "plugin", "print", "prompt", "prototype", "radio", "ref",
"regexp", "releaseevents", "reset", "resizeby", "resizeto",
"routeevent", "scroll", "scrollbars", "scrollby", "scrollto", "select",
"self", "setinterval", "settimeout", "status", "statusbar", "stop",
"string", "submit", "sun", "taint", "text", "textarea", "toolbar",
"top", "tostring", "unescape", "untaint", "unwatch", "valueof", "watch",
"window",
*/
};
/**
* The list of reserved words
*/
private static SortedSet<String> reserved = new TreeSet<String>();
/**
* For easy access ...
*/
static
{
// The Javascript reserved words array so we don't generate illegal javascript
reserved.addAll(Arrays.asList(RESERVED_ARRAY));
}
}
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