Using a generator: function *intersperse(a, delim) { let first = true; for (const x of a) { if (!first) yield delim; first = false; yield x; } } console.log([…intersperse(array, ‘&’)]); Thanks to @Bergi for pointing out the useful generalization that the input could be any iterable. If you don’t like using generators, then [].concat(…a.map(e => … Read more
Javascript’s object/property system is much more dynamic than most languages, so it’s very easy to add functionality to an object. As functions are first-class objects, they can be added to an object in exactly the same way. Object.assign is the way to add the properties of one object to another object. (Its behaviour is in … Read more
Simply provide an empty object as the target (merge supports more than one source value): var result = _.merge({}, obj, source);
You can use lodash’s _.map() with shorthand property names: const obj = { prop1 : “value”, prop2: { sub:1} }; const result = _.map(obj, (value, prop) => ({ prop, value })); console.log(result); <script src=”https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.2/lodash.min.js”></script> Or you can do it using Object#entries with Array.map() and array destructuring: const obj = { prop1 : “value”, prop2: { … Read more
This is a case of reduction for each unique element. I always use _.groupBy and then _.map the result to an array after applying the reduction. In this case the reduction operation is _.sumBy. var prjMgrValues = [ {“proj_mgr”:”Jack ProjManager”,”submitted_dollars”:12000}, {“proj_mgr”:”Jack ProjManager”,”submitted_dollars”:750000}, {“proj_mgr”:”Joe ProjManager”,”submitted_dollars”:45000} ]; var output = _(prjMgrValues) .groupBy(‘proj_mgr’) .map((objs, key) => ({ ‘proj_mgr’: … Read more
If Typescript can not deduce the type of the result of groupBy you could try asserting it yourself. function groupBy(o: any) { return o; // return any } let x = { a: 1, b: “1” } // we know better than tsc and assert the type let {a, b} = <{ a: number, b: … Read more
Check out addIndex: Creates a new list iteration function from an existing one by adding two new parameters to its callback function: the current index, and the entire list. This would turn, for instance, Ramda’s simple map function into one that more closely resembles Array.prototype.map. Note that this will only work for functions in which … Read more
Using for..in to iterate object and reduce to iterate array var data = [{costOfAirtickets: 2500, costOfHotel: 1200},{costOfAirtickets: 1500, costOfHotel: 1000}]; var result = [data.reduce((acc, n) => { for (var prop in n) { if (acc.hasOwnProperty(prop)) acc[prop] += n[prop]; else acc[prop] = n[prop]; } return acc; }, {})] console.log(result)
pydash is exactly like lodash, only for Python.
To process your response jsons in parallel you may use Promise.all: const responseJson = await response.json(); responseJson = _.sortBy(responseJson, “number”); let result = await Promise.all(_.map(responseJson, async (json) => await addEnabledProperty(json)) ); Since addEnabledProperty method is async, the following also should work (per @CRice): let result = await Promise.all(_.map(responseJson, addEnabledProperty));