Map function 从过滤后的 object 构建一个数组

Question

I'm trying to get my head around map functions currently without much success.

I currently have a list of objects and am trying to remap to a new object using the map function to return a map indexed by the created property with a list of wooids.

Having written my map function, I only seem to be returning the last time.

 const variants = [ { created: '2022-03-06', hashname: 'c78ba80402290724609a5e98c369c90984494152', hashobject: '80864e6329d5e305a512ace872ad7d56a3f41095', hashparent: '19c5d50ddddeb7c9a92469df78c47d9d611f1599', action: 'added', wooid: 7288 }, { created: '2022-03-06', hashname: 'c78ba80402290724609a5e98c369c90984494152', hashobject: '80864e6329d5e305a512ace872ad7d56a3f41095', hashparent: '19c5d50ddddeb7c9a92469df78c47d9d611f1599', action: 'added', wooid: 7289 } ] const res = Object.fromEntries(variants.map(k => [k.created, [k.wooid]])) console.log(res)

Current output

{ '2022-03-06': [ 7289, 7288 ] }

Desired output:

 { '2022-03-06': [ 7289, 7288 ] }

Any help would be greatly appreciated as I'm unsure how to dynamically populate the array to include all other entires (6 in total).

Answer 1

Use Array.prototype.reduce() to build up your object. Check if you already have a key for each created value and if not, create an empty array. Then append the wooid value

 const variants = [{"created":"2022-03-06","hashname":"c78ba80402290724609a5e98c369c90984494152","hashobject":"80864e6329d5e305a512ace872ad7d56a3f41095","hashparent":"19c5d50ddddeb7c9a92469df78c47d9d611f1599","action":"added","wooid":7288},{"created":"2022-03-06","hashname":"c78ba80402290724609a5e98c369c90984494152","hashobject":"80864e6329d5e305a512ace872ad7d56a3f41095","hashparent":"19c5d50ddddeb7c9a92469df78c47d9d611f1599","action":"added","wooid":7289}] const res = variants.reduce((acc, { created, wooid }) => ({...acc, [ created ]: [...acc[created]?? [], // init to an empty array if unset wooid ] }), {}) console.log(res)

This will collect wooid values by created in the order they appear in the original data.