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replacer
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@douglascrockford
douglascrockford committed May 7, 2016
1 parent a48e0c7 commit ff3f641
Showing 1 changed file with 72 additions and 62 deletions.
134 changes: 72 additions & 62 deletions cycle.js
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
/*
cycle.js
2015-02-25
2016-05-01
Public Domain.
Expand All @@ -15,60 +15,75 @@

/*jslint eval, for */

/*property
$ref, apply, call, decycle, hasOwnProperty, length, prototype, push,
retrocycle, stringify, test, toString
/*property
$ref, decycle, forEach, isArray, keys, length, push, retrocycle, stringify,
test
*/

if (typeof JSON.decycle !== 'function') {
JSON.decycle = function decycle(object) {
'use strict';
if (typeof JSON.decycle !== "function") {
JSON.decycle = function decycle(object, replacer) {
"use strict";

// Make a deep copy of an object or array, assuring that there is at most
// one instance of each object or array in the resulting structure. The
// duplicate references (which might be forming cycles) are replaced with
// an object of the form
// {$ref: PATH}

// {"$ref": PATH}

// where the PATH is a JSONPath string that locates the first occurance.

// So,

// var a = [];
// a[0] = a;
// return JSON.stringify(JSON.decycle(a));

// produces the string '[{"$ref":"$"}]'.

// If a replacer function is provided, then it will be called for each value.
// A replacer function receives a value and returns a replacement value.

// JSONPath is used to locate the unique object. $ indicates the top level of
// the object or array. [NUMBER] or [STRING] indicates a child member or
// the object or array. [NUMBER] or [STRING] indicates a child element or
// property.

var objects = [], // Keep a reference to each unique object or array
paths = []; // Keep the path to each unique object or array
var objects = []; // Keep a reference to each unique object or array
var paths = []; // Keep the path to each unique object or array

return (function derez(value, path) {

// The derez recurses through the object, producing the deep copy.
// The derez function recurses through the object, producing the deep copy.

var i; // The loop counter
var nu; // The new object or array

var i, // The loop counter
name, // Property name
nu; // The new object or array
// If a replacer function was provided, then call it to get a replacement value.

// typeof null === 'object', so go on if this value is really an object but not
if (replacer !== undefined) {
value = replacer(value);
}

// typeof null === "object", so go on if this value is really an object but not
// one of the weird builtin objects.

if (typeof value === 'object' && value !== null &&
!(value instanceof Boolean) &&
!(value instanceof Date) &&
!(value instanceof Number) &&
!(value instanceof RegExp) &&
!(value instanceof String)) {
if (
typeof value === "object" && value !== null &&
!(value instanceof Boolean) &&
!(value instanceof Date) &&
!(value instanceof Number) &&
!(value instanceof RegExp) &&
!(value instanceof String)
) {

// If the value is an object or array, look to see if we have already
// encountered it. If so, return a $ref/path object. This is a hard way,
// encountered it. If so, return a {"$ref":PATH} object. This is a hard
// linear search that will get slower as the number of unique objects grows.
// Someday, this should be replaced with an ES6 WeakMap.

for (i = 0; i < objects.length; i += 1) {
if (objects[i] === value) {
return {$ref: paths[i]};
}
i = objects.indexOf(value);
if (i >= 0) {
return {$ref: paths[i]};
}

// Otherwise, accumulate the unique value and its path.
Expand All @@ -78,34 +93,34 @@ if (typeof JSON.decycle !== 'function') {

// If it is an array, replicate the array.

if (Object.prototype.toString.apply(value) === '[object Array]') {
if (Array.isArray(value)) {
nu = [];
for (i = 0; i < value.length; i += 1) {
nu[i] = derez(value[i], path + '[' + i + ']');
}
value.forEach(function (element, i) {
nu[i] = derez(element, path + "[" + i + "]");
});
} else {

// If it is an object, replicate the object.

nu = {};
for (name in value) {
if (Object.prototype.hasOwnProperty.call(value, name)) {
nu[name] = derez(value[name],
path + '[' + JSON.stringify(name) + ']');
}
}
Object.keys(value).forEach(function (name) {
nu[name] = derez(
value[name],
path + "[" + JSON.stringify(name) + "]"
);
});
}
return nu;
}
return value;
}(object, '$'));
}(object, "$"));
};
}


if (typeof JSON.retrocycle !== 'function') {
if (typeof JSON.retrocycle !== "function") {
JSON.retrocycle = function retrocycle($) {
'use strict';
"use strict";

// Restore an object that was reduced by decycle. Members whose values are
// objects of the form
Expand Down Expand Up @@ -135,35 +150,30 @@ if (typeof JSON.retrocycle !== 'function') {
// replaces the $ref object with a reference to the value that is found by
// the path.

var i, item, name, path;

if (value && typeof value === 'object') {
if (Object.prototype.toString.apply(value) === '[object Array]') {
for (i = 0; i < value.length; i += 1) {
item = value[i];
if (item && typeof item === 'object') {
path = item.$ref;
if (typeof path === 'string' && px.test(path)) {
if (value && typeof value === "object") {
if (Array.isArray(value)) {
value.forEach(function (element, i) {
if (typeof element === "object" && element !== null) {
var path = element.$ref;
if (typeof path === "string" && px.test(path)) {
value[i] = eval(path);
} else {
rez(item);
rez(element);
}
}
}
});
} else {
for (name in value) {
if (typeof value[name] === 'object') {
item = value[name];
if (item) {
path = item.$ref;
if (typeof path === 'string' && px.test(path)) {
value[name] = eval(path);
} else {
rez(item);
}
Object.keys(value).forEach(function (name) {
var item = value[name];
if (typeof item === "object" && item !== null) {
var path = item.$ref;
if (typeof path === "string" && px.test(path)) {
value[name] = eval(path);
} else {
rez(item);
}
}
}
});
}
}
}($));
Expand Down

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