Created
April 19, 2019 18:17
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Creates a new object that watches for changes on its properties
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| /** | |
| * Callback whenever a property in the object changes | |
| * @callback onChangeCallback | |
| * @param {*} newValue | |
| * @param {*} oldValue | |
| * @param {String} path | |
| */ | |
| /** | |
| * Creates a new object that is watched for changes | |
| * Works recursively as long as children are objects | |
| * Will not work for newly defined properties | |
| * | |
| * NOTE: Returning a new object instead of modifying | |
| * orignal boosts performance by over 20x | |
| * | |
| * @param {Object} obj | |
| * @param {onChangeCallback} callback | |
| * @return {Object} | |
| */ | |
| const onChange = (obj, callback, pathPrefix = "") => { | |
| const newObj = {}; | |
| const privateData = {}; | |
| const keys = Object.keys(obj); | |
| for (let i = 0; i < keys.length; ++i) { | |
| const key = keys[i]; | |
| let value = obj[key]; | |
| if (typeof value === "object") { | |
| value = onChange(value, callback, `${key}.`); | |
| } | |
| // save key to privateData | |
| privateData[key] = value; | |
| // replace key with getter/setter pointing to privateData | |
| Object.defineProperty(newObj, key, { | |
| enumerable: true, | |
| get() { | |
| return privateData[key]; | |
| }, | |
| set(newValue) { | |
| const oldValue = privateData[key]; | |
| privateData[key] = newValue; | |
| callback(newValue, oldValue, pathPrefix + key); | |
| }, | |
| }); | |
| } | |
| return newObj; | |
| }; | |
| export default onChange; |
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