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1 /*
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2 cycle.js
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3 2012-08-19
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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 code should be minified before deployment.
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10 See http://javascript.crockford.com/jsmin.html
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11
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12 USE YOUR OWN COPY. IT IS EXTREMELY UNWISE TO LOAD CODE FROM SERVERS YOU DO
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13 NOT CONTROL.
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14 */
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15
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16 /*jslint evil: true, regexp: true */
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17
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18 /*members $ref, apply, call, decycle, hasOwnProperty, length, prototype, push,
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19 retrocycle, stringify, test, toString
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20 */
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21
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22 if (typeof JSON.decycle !== 'function') {
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23 JSON.decycle = function decycle(object) {
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24 'use strict';
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25
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26 // Make a deep copy of an object or array, assuring that there is at most
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27 // one instance of each object or array in the resulting structure. The
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28 // duplicate references (which might be forming cycles) are replaced with
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29 // an object of the form
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30 // {$ref: PATH}
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31 // where the PATH is a JSONPath string that locates the first occurance.
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32 // So,
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33 // var a = [];
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34 // a[0] = a;
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35 // return JSON.stringify(JSON.decycle(a));
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36 // produces the string '[{"$ref":"$"}]'.
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37
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38 // JSONPath is used to locate the unique object. $ indicates the top level of
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39 // the object or array. [NUMBER] or [STRING] indicates a child member or
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40 // property.
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41
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42 var objects = [], // Keep a reference to each unique object or array
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43 paths = []; // Keep the path to each unique object or array
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44
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45 return (function derez(value, path) {
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46
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47 // The derez recurses through the object, producing the deep copy.
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48
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49 var i, // The loop counter
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50 name, // Property name
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51 nu; // The new object or array
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52
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53 switch (typeof value) {
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54 case 'object':
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55
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56 // typeof null === 'object', so get out if this value is not really an object.
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57 // Also get out if it is a weird builtin object.
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58
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59 if (value === null ||
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60 value instanceof Boolean ||
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61 value instanceof Date ||
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62 value instanceof Number ||
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63 value instanceof RegExp ||
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64 value instanceof String) {
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65 return value;
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66 }
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67
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68 // If the value is an object or array, look to see if we have already
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69 // encountered it. If so, return a $ref/path object. This is a hard way,
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70 // linear search that will get slower as the number of unique objects grows.
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71
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72 for (i = 0; i < objects.length; i += 1) {
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73 if (objects[i] === value) {
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74 return {$ref: paths[i]};
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75 }
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76 }
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77
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78 // Otherwise, accumulate the unique value and its path.
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79
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80 objects.push(value);
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81 paths.push(path);
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82
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83 // If it is an array, replicate the array.
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84
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85 if (Object.prototype.toString.apply(value) === '[object Array]') {
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86 nu = [];
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87 for (i = 0; i < value.length; i += 1) {
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88 nu[i] = derez(value[i], path + '[' + i + ']');
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89 }
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90 } else {
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91
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92 // If it is an object, replicate the object.
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93
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94 nu = {};
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95 for (name in value) {
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96 if (Object.prototype.hasOwnProperty.call(value, name)) {
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97 nu[name] = derez(value[name],
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98 path + '[' + JSON.stringify(name) + ']');
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99 }
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100 }
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101 }
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102 return nu;
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103 case 'number':
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104 case 'string':
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105 case 'boolean':
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106 return value;
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107 }
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108 }(object, '$'));
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109 };
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110 }
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111
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112
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113 if (typeof JSON.retrocycle !== 'function') {
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114 JSON.retrocycle = function retrocycle($) {
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115 'use strict';
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116
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117 // Restore an object that was reduced by decycle. Members whose values are
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118 // objects of the form
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119 // {$ref: PATH}
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120 // are replaced with references to the value found by the PATH. This will
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121 // restore cycles. The object will be mutated.
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122
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123 // The eval function is used to locate the values described by a PATH. The
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124 // root object is kept in a $ variable. A regular expression is used to
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125 // assure that the PATH is extremely well formed. The regexp contains nested
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126 // * quantifiers. That has been known to have extremely bad performance
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127 // problems on some browsers for very long strings. A PATH is expected to be
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128 // reasonably short. A PATH is allowed to belong to a very restricted subset of
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129 // Goessner's JSONPath.
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130
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131 // So,
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132 // var s = '[{"$ref":"$"}]';
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133 // return JSON.retrocycle(JSON.parse(s));
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134 // produces an array containing a single element which is the array itself.
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135
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136 var px =
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137 /^\$(?:\[(?:\d+|\"(?:[^\\\"\u0000-\u001f]|\\([\\\"\/bfnrt]|u[0-9a-zA-Z]{4}))*\")\])*$/;
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138
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139 (function rez(value) {
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140
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141 // The rez function walks recursively through the object looking for $ref
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142 // properties. When it finds one that has a value that is a path, then it
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143 // replaces the $ref object with a reference to the value that is found by
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144 // the path.
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145
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146 var i, item, name, path;
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147
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148 if (value && typeof value === 'object') {
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149 if (Object.prototype.toString.apply(value) === '[object Array]') {
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150 for (i = 0; i < value.length; i += 1) {
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151 item = value[i];
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152 if (item && typeof item === 'object') {
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153 path = item.$ref;
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154 if (typeof path === 'string' && px.test(path)) {
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155 value[i] = eval(path);
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156 } else {
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157 rez(item);
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158 }
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159 }
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160 }
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161 } else {
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162 for (name in value) {
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163 if (typeof value[name] === 'object') {
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164 item = value[name];
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165 if (item) {
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166 path = item.$ref;
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167 if (typeof path === 'string' && px.test(path)) {
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168 value[name] = eval(path);
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169 } else {
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170 rez(item);
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171 }
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172 }
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173 }
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174 }
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175 }
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176 }
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177 }($));
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178 return $;
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179 };
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180 }
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