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1 /*
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2 json_parse.js
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3 2012-06-20
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4
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5 Public Domain.
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6
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7 NO WARRANTY EXPRESSED OR IMPLIED. USE AT YOUR OWN RISK.
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8
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9 This file creates a json_parse function.
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10
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11 json_parse(text, reviver)
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12 This method parses a JSON text to produce an object or array.
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13 It can throw a SyntaxError exception.
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14
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15 The optional reviver parameter is a function that can filter and
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16 transform the results. It receives each of the keys and values,
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17 and its return value is used instead of the original value.
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18 If it returns what it received, then the structure is not modified.
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19 If it returns undefined then the member is deleted.
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20
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21 Example:
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22
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23 // Parse the text. Values that look like ISO date strings will
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24 // be converted to Date objects.
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25
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26 myData = json_parse(text, function (key, value) {
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27 var a;
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28 if (typeof value === 'string') {
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29 a =
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30 /^(\d{4})-(\d{2})-(\d{2})T(\d{2}):(\d{2}):(\d{2}(?:\.\d*)?)Z$/.exec(value);
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31 if (a) {
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32 return new Date(Date.UTC(+a[1], +a[2] - 1, +a[3], +a[4],
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33 +a[5], +a[6]));
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34 }
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35 }
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36 return value;
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37 });
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38
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39 This is a reference implementation. You are free to copy, modify, or
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40 redistribute.
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41
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42 This code should be minified before deployment.
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43 See http://javascript.crockford.com/jsmin.html
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44
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45 USE YOUR OWN COPY. IT IS EXTREMELY UNWISE TO LOAD CODE FROM SERVERS YOU DO
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46 NOT CONTROL.
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47 */
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48
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49 /*members "", "\"", "\/", "\\", at, b, call, charAt, f, fromCharCode,
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50 hasOwnProperty, message, n, name, prototype, push, r, t, text
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51 */
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52
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53 var json_parse = (function () {
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54 "use strict";
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55
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56 // This is a function that can parse a JSON text, producing a JavaScript
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57 // data structure. It is a simple, recursive descent parser. It does not use
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58 // eval or regular expressions, so it can be used as a model for implementing
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59 // a JSON parser in other languages.
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60
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61 // We are defining the function inside of another function to avoid creating
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62 // global variables.
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63
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64 var at, // The index of the current character
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65 ch, // The current character
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66 escapee = {
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67 '"': '"',
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68 '\\': '\\',
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69 '/': '/',
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70 b: '\b',
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71 f: '\f',
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72 n: '\n',
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73 r: '\r',
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74 t: '\t'
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75 },
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76 text,
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77
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78 error = function (m) {
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79
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80 // Call error when something is wrong.
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81
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82 throw {
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83 name: 'SyntaxError',
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84 message: m,
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85 at: at,
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86 text: text
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87 };
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88 },
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89
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90 next = function (c) {
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91
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92 // If a c parameter is provided, verify that it matches the current character.
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93
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94 if (c && c !== ch) {
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95 error("Expected '" + c + "' instead of '" + ch + "'");
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96 }
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97
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98 // Get the next character. When there are no more characters,
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99 // return the empty string.
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100
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101 ch = text.charAt(at);
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102 at += 1;
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103 return ch;
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104 },
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105
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106 number = function () {
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107
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108 // Parse a number value.
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109
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110 var number,
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111 string = '';
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112
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113 if (ch === '-') {
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114 string = '-';
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115 next('-');
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116 }
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117 while (ch >= '0' && ch <= '9') {
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118 string += ch;
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119 next();
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120 }
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121 if (ch === '.') {
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122 string += '.';
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123 while (next() && ch >= '0' && ch <= '9') {
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124 string += ch;
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125 }
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126 }
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127 if (ch === 'e' || ch === 'E') {
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128 string += ch;
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129 next();
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130 if (ch === '-' || ch === '+') {
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131 string += ch;
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132 next();
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133 }
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134 while (ch >= '0' && ch <= '9') {
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135 string += ch;
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136 next();
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137 }
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138 }
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139 number = +string;
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140 if (!isFinite(number)) {
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141 error("Bad number");
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142 } else {
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143 return number;
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144 }
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145 },
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146
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147 string = function () {
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148
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149 // Parse a string value.
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150
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151 var hex,
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152 i,
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153 string = '',
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154 uffff;
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155
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156 // When parsing for string values, we must look for " and \ characters.
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157
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158 if (ch === '"') {
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159 while (next()) {
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160 if (ch === '"') {
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161 next();
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162 return string;
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163 }
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164 if (ch === '\\') {
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165 next();
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166 if (ch === 'u') {
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167 uffff = 0;
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168 for (i = 0; i < 4; i += 1) {
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169 hex = parseInt(next(), 16);
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170 if (!isFinite(hex)) {
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171 break;
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172 }
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173 uffff = uffff * 16 + hex;
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174 }
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175 string += String.fromCharCode(uffff);
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176 } else if (typeof escapee[ch] === 'string') {
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177 string += escapee[ch];
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178 } else {
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179 break;
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180 }
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181 } else {
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182 string += ch;
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183 }
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184 }
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185 }
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186 error("Bad string");
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187 },
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188
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189 white = function () {
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190
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191 // Skip whitespace.
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192
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193 while (ch && ch <= ' ') {
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194 next();
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195 }
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196 },
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197
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198 word = function () {
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199
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200 // true, false, or null.
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201
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202 switch (ch) {
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203 case 't':
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204 next('t');
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205 next('r');
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206 next('u');
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207 next('e');
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208 return true;
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209 case 'f':
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210 next('f');
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211 next('a');
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212 next('l');
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213 next('s');
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214 next('e');
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215 return false;
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216 case 'n':
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217 next('n');
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218 next('u');
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219 next('l');
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220 next('l');
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221 return null;
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222 }
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223 error("Unexpected '" + ch + "'");
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224 },
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225
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226 value, // Place holder for the value function.
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227
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228 array = function () {
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229
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230 // Parse an array value.
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231
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232 var array = [];
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233
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234 if (ch === '[') {
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235 next('[');
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236 white();
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237 if (ch === ']') {
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238 next(']');
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239 return array; // empty array
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240 }
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241 while (ch) {
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242 array.push(value());
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243 white();
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244 if (ch === ']') {
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245 next(']');
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246 return array;
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247 }
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248 next(',');
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249 white();
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250 }
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251 }
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252 error("Bad array");
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253 },
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254
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255 object = function () {
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256
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257 // Parse an object value.
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258
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259 var key,
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260 object = {};
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261
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262 if (ch === '{') {
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263 next('{');
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264 white();
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265 if (ch === '}') {
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266 next('}');
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267 return object; // empty object
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268 }
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269 while (ch) {
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270 key = string();
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271 white();
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272 next(':');
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273 if (Object.hasOwnProperty.call(object, key)) {
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274 error('Duplicate key "' + key + '"');
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275 }
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276 object[key] = value();
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277 white();
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278 if (ch === '}') {
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279 next('}');
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280 return object;
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281 }
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282 next(',');
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283 white();
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284 }
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285 }
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286 error("Bad object");
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287 };
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288
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289 value = function () {
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290
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291 // Parse a JSON value. It could be an object, an array, a string, a number,
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292 // or a word.
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293
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294 white();
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295 switch (ch) {
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296 case '{':
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297 return object();
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298 case '[':
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299 return array();
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300 case '"':
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301 return string();
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302 case '-':
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303 return number();
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304 default:
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305 return ch >= '0' && ch <= '9' ? number() : word();
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306 }
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307 };
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308
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309 // Return the json_parse function. It will have access to all of the above
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310 // functions and variables.
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311
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312 return function (source, reviver) {
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313 var result;
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314
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315 text = source;
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316 at = 0;
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317 ch = ' ';
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318 result = value();
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319 white();
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320 if (ch) {
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321 error("Syntax error");
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322 }
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323
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324 // If there is a reviver function, we recursively walk the new structure,
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325 // passing each name/value pair to the reviver function for possible
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326 // transformation, starting with a temporary root object that holds the result
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327 // in an empty key. If there is not a reviver function, we simply return the
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328 // result.
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329
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330 return typeof reviver === 'function'
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331 ? (function walk(holder, key) {
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332 var k, v, value = holder[key];
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333 if (value && typeof value === 'object') {
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334 for (k in value) {
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335 if (Object.prototype.hasOwnProperty.call(value, k)) {
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336 v = walk(value, k);
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337 if (v !== undefined) {
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338 value[k] = v;
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339 } else {
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340 delete value[k];
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341 }
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342 }
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343 }
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344 }
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345 return reviver.call(holder, key, value);
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346 }({'': result}, ''))
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347 : result;
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348 };
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349 }());
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