80 lines
2.8 KiB
JavaScript
80 lines
2.8 KiB
JavaScript
// Based on https://github.com/dscape/cycle/blob/master/cycle.js
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module.exports = function decycle(object) {
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// Make a deep copy of an object or array, assuring that there is at most
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// one instance of each object or array in the resulting structure. The
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// duplicate references (which might be forming cycles) are replaced with
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// an object of the form
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// {$ref: PATH}
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// where the PATH is a JSONPath string that locates the first occurance.
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// So,
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// var a = [];
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// a[0] = a;
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// return JSON.stringify(JSON.decycle(a));
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// produces the string '[{"$ref":"$"}]'.
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// JSONPath is used to locate the unique object. $ indicates the top level of
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// the object or array. [NUMBER] or [STRING] indicates a child member or
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// property.
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var objects = [], // Keep a reference to each unique object or array
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paths = []; // Keep the path to each unique object or array
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return (function derez(value, path) {
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// The derez recurses through the object, producing the deep copy.
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var i, // The loop counter
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name, // Property name
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nu; // The new object or array
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// typeof null === 'object', so go on if this value is really an object but not
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// one of the weird builtin objects.
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if (typeof value === 'object' && value !== null &&
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!(value instanceof Boolean) &&
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!(value instanceof Date) &&
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!(value instanceof Number) &&
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!(value instanceof RegExp) &&
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!(value instanceof String)) {
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// If the value is an object or array, look to see if we have already
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// encountered it. If so, return a $ref/path object. This is a hard way,
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// linear search that will get slower as the number of unique objects grows.
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for (i = 0; i < objects.length; i += 1) {
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if (objects[i] === value) {
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return {$ref: paths[i]};
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}
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}
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// Otherwise, accumulate the unique value and its path.
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objects.push(value);
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paths.push(path);
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// If it is an array, replicate the array.
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if (Object.prototype.toString.apply(value) === '[object Array]') {
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nu = [];
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for (i = 0; i < value.length; i += 1) {
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nu[i] = derez(value[i], path + '[' + i + ']');
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}
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} else {
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// If it is an object, replicate the object.
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nu = {};
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for (name in value) {
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if (Object.prototype.hasOwnProperty.call(value, name)) {
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nu[name] = derez(value[name],
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path + '[' + JSON.stringify(name) + ']');
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}
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}
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}
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return nu;
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}
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return value;
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}(object, '$'));
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};
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