103 lines
2.8 KiB
JavaScript
103 lines
2.8 KiB
JavaScript
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'use strict';
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/**
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* a collection of cloning functions
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*/
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/**
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* a no-op placeholder which returns the given object unchanged
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* useful for when a clone function needs to be passed but cloning is not
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* required
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* @param obj the input object
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* @return the input object, unchanged
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*/
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function nop(obj) {
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return obj;
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}
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/**
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* clones the given object using JSON.parse and JSON.stringify
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* @param obj the object to clone
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* @return the cloned object
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*/
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function clone(obj) {
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return JSON.parse(JSON.stringify(obj));
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}
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/**
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* clones the given object's properties shallowly, ignores properties from prototype
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* @param obj the object to clone
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* @return the cloned object
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*/
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function shallowClone(obj) {
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let result = {};
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for (let p in obj) {
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if (obj.hasOwnProperty(p)) {
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result[p] = obj[p];
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}
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}
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return result;
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}
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/**
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* clones the given object's properties deeply, ignores properties from prototype
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* @param obj the object to clone
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* @return the cloned object
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*/
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function deepClone(obj) {
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let result = Array.isArray(obj) ? [] : {};
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for (let p in obj) {
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if (obj.hasOwnProperty(p) || Array.isArray(obj)) {
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result[p] = (typeof obj[p] === 'object') ? deepClone(obj[p]) : obj[p];
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}
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}
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return result;
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}
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/**
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* clones the given object's properties shallowly, using Object.assign
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* @param obj the object to clone
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* @return the cloned object
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*/
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function fastClone(obj) {
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return Object.assign({},obj);
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}
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/**
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* Source: stackoverflow http://bit.ly/2A1Kha6
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*/
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function circularClone(obj, hash) {
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if (!hash) hash = new WeakMap();
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// Do not try to clone primitives or functions
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if (Object(obj) !== obj || obj instanceof Function) return obj;
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if (hash.has(obj)) return hash.get(obj); // Cyclic reference
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try { // Try to run constructor (without arguments, as we don't know them)
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var result = new obj.constructor();
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} catch(e) { // Constructor failed, create object without running the constructor
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result = Object.create(Object.getPrototypeOf(obj));
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}
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// Optional: support for some standard constructors (extend as desired)
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/*if (obj instanceof Map)
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Array.from(obj, ([key, val]) => result.set(circularClone(key, hash),
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circularClone(val, hash)) );
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else if (obj instanceof Set)
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Array.from(obj, (key) => result.add(circularClone(key, hash)) );
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*/
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// Register in hash
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hash.set(obj, result);
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// Clone and assign enumerable own properties recursively
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return Object.assign(result, ...Object.keys(obj).map (
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key => ({ [key]: circularClone(obj[key], hash) }) ));
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}
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module.exports = {
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nop : nop,
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clone : clone,
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shallowClone : shallowClone,
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deepClone : deepClone,
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fastClone : fastClone,
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circularClone : circularClone
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};
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