Unescapes any JavaScript literals found in the String. - Java Scripting

Java examples for Scripting:Javascript

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Description

Unescapes any JavaScript literals found in the String.

Demo Code

/*//from  w  w w.j ava 2 s  .  com
 * 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.
 */
//package com.java2s;

public class Main {
    /**
     * <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 chacater
                    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();
    }
}

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