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json_parse = (function () {
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// This is a function that can parse a JSON text, producing a JavaScript
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// data structure. It is a simple, recursive descent parser. It does not use
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// eval or regular expressions, so it can be used as a model for implementing
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// a JSON parser in other languages.
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// We are defining the function inside of another function to avoid creating
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// global variables.
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var at, // The index of the current character
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ch, // The current character
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escapee = {
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'"': '"',
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'\\': '\\',
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'/': '/',
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b: '\b',
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f: '\f',
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n: '\n',
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r: '\r',
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t: '\t'
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},
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text,
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error = function (m) {
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// Call error when something is wrong.
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throw {
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name: 'SyntaxError',
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message: m,
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at: at,
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text: text
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};
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},
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next = function (c) {
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// If a c parameter is provided, verify that it matches the current character.
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if (c && c !== ch) {
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error("Expected '" + c + "' instead of '" + ch + "'");
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}
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// Get the next character. When there are no more characters,
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// return the empty string.
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ch = text.charAt(at);
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at += 1;
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return ch;
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},
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number = function () {
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// Parse a number value.
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var number,
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string = '';
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if (ch === '-') {
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string = '-';
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next('-');
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}
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while (ch >= '0' && ch <= '9') {
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string += ch;
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next();
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}
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if (ch === '.') {
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string += '.';
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while (next() && ch >= '0' && ch <= '9') {
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string += ch;
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}
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}
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if (ch === 'e' || ch === 'E') {
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string += ch;
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next();
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if (ch === '-' || ch === '+') {
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string += ch;
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next();
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}
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while (ch >= '0' && ch <= '9') {
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string += ch;
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next();
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}
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}
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number = +string;
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if (isNaN(number)) {
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error("Bad number");
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} else {
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return number;
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}
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},
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string = function () {
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// Parse a string value.
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var hex,
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i,
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string = '',
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uffff;
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// When parsing for string values, we must look for " and \ characters.
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if (ch === '"') {
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while (next()) {
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if (ch === '"') {
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next();
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return string;
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} else if (ch === '\\') {
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next();
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if (ch === 'u') {
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uffff = 0;
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for (i = 0; i < 4; i += 1) {
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hex = parseInt(next(), 16);
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if (!isFinite(hex)) {
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break;
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}
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uffff = uffff * 16 + hex;
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}
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string += String.fromCharCode(uffff);
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} else if (typeof escapee[ch] === 'string') {
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string += escapee[ch];
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} else {
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break;
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}
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} else {
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string += ch;
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}
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}
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}
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error("Bad string");
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},
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white = function () {
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// Skip whitespace.
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while (ch && ch <= ' ') {
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next();
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}
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},
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word = function () {
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// true, false, or null.
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switch (ch) {
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case 't':
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next('t');
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next('r');
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next('u');
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next('e');
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return true;
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case 'f':
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next('f');
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next('a');
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next('l');
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next('s');
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next('e');
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return false;
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case 'n':
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next('n');
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next('u');
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next('l');
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next('l');
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return null;
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}
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error("Unexpected '" + ch + "'");
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},
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value, // Place holder for the value function.
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array = function () {
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// Parse an array value.
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var array = [];
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if (ch === '[') {
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next('[');
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white();
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if (ch === ']') {
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next(']');
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return array; // empty array
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}
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while (ch) {
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array.push(value());
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white();
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if (ch === ']') {
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next(']');
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return array;
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}
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next(',');
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white();
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}
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}
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error("Bad array");
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},
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object = function () {
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// Parse an object value.
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var key,
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object = {};
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if (ch === '{') {
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next('{');
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white();
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if (ch === '}') {
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next('}');
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return object; // empty object
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}
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while (ch) {
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key = string();
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white();
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next(':');
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if (Object.hasOwnProperty.call(object, key)) {
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error('Duplicate key "' + key + '"');
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}
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object[key] = value();
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white();
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if (ch === '}') {
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next('}');
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return object;
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}
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next(',');
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white();
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}
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}
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error("Bad object");
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};
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value = function () {
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// Parse a JSON value. It could be an object, an array, a string, a number,
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// or a word.
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white();
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switch (ch) {
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case '{':
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return object();
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case '[':
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return array();
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case '"':
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return string();
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case '-':
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return number();
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default:
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return ch >= '0' && ch <= '9' ? number() : word();
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}
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};
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// Return the json_parse function. It will have access to all of the above
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// functions and variables.
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return function (source, reviver) {
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var result;
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text = source;
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at = 0;
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ch = ' ';
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result = value();
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white();
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if (ch) {
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error("Syntax error");
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}
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// If there is a reviver function, we recursively walk the new structure,
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// passing each name/value pair to the reviver function for possible
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// transformation, starting with a temporary root object that holds the result
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// in an empty key. If there is not a reviver function, we simply return the
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// result.
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return typeof reviver === 'function' ? (function walk(holder, key) {
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var k, v, value = holder[key];
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if (value && typeof value === 'object') {
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for (k in value) {
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if (Object.hasOwnProperty.call(value, k)) {
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v = walk(value, k);
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if (v !== undefined) {
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value[k] = v;
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} else {
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delete value[k];
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}
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}
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}
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}
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return reviver.call(holder, key, value);
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}({'': result}, '')) : result;
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};
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}());
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