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/**
* @file obj.js
* @module obj
*/
/**
* @callback obj:EachCallback
*
* @param {*} value
* The current key for the object that is being iterated over.
*
* @param {string} key
* The current key-value for object that is being iterated over
*/
/**
* @callback obj:ReduceCallback
*
* @param {*} accum
* The value that is accumulating over the reduce loop.
*
* @param {*} value
* The current key for the object that is being iterated over.
*
* @param {string} key
* The current key-value for object that is being iterated over
*
* @return {*}
* The new accumulated value.
*/
const toString = Object.prototype.toString;
/**
* Get the keys of an Object
*
* @param {Object}
* The Object to get the keys from
*
* @return {string[]}
* An array of the keys from the object. Returns an empty array if the
* object passed in was invalid or had no keys.
*
* @private
*/
const keys = function(object) {
return isObject(object) ? Object.keys(object) : [];
};
/**
* Array-like iteration for objects.
*
* @param {Object} object
* The object to iterate over
*
* @param {obj:EachCallback} fn
* The callback function which is called for each key in the object.
*/
export function each(object, fn) {
keys(object).forEach(key => fn(object[key], key));
}
/**
* Array-like reduce for objects.
*
* @param {Object} object
* The Object that you want to reduce.
*
* @param {Function} fn
* A callback function which is called for each key in the object. It
* receives the accumulated value and the per-iteration value and key
* as arguments.
*
* @param {*} [initial = 0]
* Starting value
*
* @return {*}
* The final accumulated value.
*/
export function reduce(object, fn, initial = 0) {
return keys(object).reduce((accum, key) => fn(accum, object[key], key), initial);
}
/**
* Returns whether a value is an object of any kind - including DOM nodes,
* arrays, regular expressions, etc. Not functions, though.
*
* This avoids the gotcha where using `typeof` on a `null` value
* results in `'object'`.
*
* @param {Object} value
* @return {boolean}
*/
export function isObject(value) {
return !!value && typeof value === 'object';
}
/**
* Returns whether an object appears to be a "plain" object - that is, a
* direct instance of `Object`.
*
* @param {Object} value
* @return {boolean}
*/
export function isPlain(value) {
return isObject(value) &&
toString.call(value) === '[object Object]' &&
value.constructor === Object;
}
/**
* Merge two objects recursively.
*
* Performs a deep merge like
* {@link https://lodash.com/docs/4.17.10#merge|lodash.merge}, but only merges
* plain objects (not arrays, elements, or anything else).
*
* Non-plain object values will be copied directly from the right-most
* argument.
*
* @param {Object[]} sources
* One or more objects to merge into a new object.
*
* @return {Object}
* A new object that is the merged result of all sources.
*/
export function merge(...sources) {
const result = {};
sources.forEach(source => {
if (!source) {
return;
}
each(source, (value, key) => {
if (!isPlain(value)) {
result[key] = value;
return;
}
if (!isPlain(result[key])) {
result[key] = {};
}
result[key] = merge(result[key], value);
});
});
return result;
}
/**
* Returns an array of values for a given object
*
* @param {Object} source - target object
* @return {Array<unknown>} - object values
*/
export function values(source = {}) {
const result = [];
for (const key in source) {
if (source.hasOwnProperty(key)) {
const value = source[key];
result.push(value);
}
}
return result;
}
/**
* Object.defineProperty but "lazy", which means that the value is only set after
* it is retrieved the first time, rather than being set right away.
*
* @param {Object} obj the object to set the property on
* @param {string} key the key for the property to set
* @param {Function} getValue the function used to get the value when it is needed.
* @param {boolean} setter whether a setter should be allowed or not
*/
export function defineLazyProperty(obj, key, getValue, setter = true) {
const set = (value) =>
Object.defineProperty(obj, key, {value, enumerable: true, writable: true});
const options = {
configurable: true,
enumerable: true,
get() {
const value = getValue();
set(value);
return value;
}
};
if (setter) {
options.set = set;
}
return Object.defineProperty(obj, key, options);
}
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