Dynamically call function with multiple arguments

Question

I'm trying to find similar items amongs a dynamic amount of arrays, For example I might have 2 or 3 arrays with data in them, and want to find the which items exist between all of them.

At the minute i've got this "working" but really ugly code which won't scale past 3 items. The GDAX, PLNX etc are all bools which I have available to tell me whether this option is selected.

The intersectionBy is a lodash helper function with further information available here https://lodash.com/docs/4.17.4#intersectionBy

  let similarItems = [];
  similarItems = GDAX && PLNX && BTRX ? _.intersectionBy(data.BTRX, data.PLNX, data.GDAX, 'pair') : similarItems;
  similarItems = GDAX && PLNX && !BTRX ? _.intersectionBy(data.PLNX, data.GDAX, 'pair') : similarItems;
  similarItems = GDAX && !PLNX && BTRX ? _.intersectionBy(data.BTRX, data.GDAX, 'pair') : similarItems;
  similarItems = !GDAX && PLNX && BTRX ? _.intersectionBy(data.BTRX, data.PLNX, 'pair') : similarItems;

smnbbrv · Accepted Answer · 2018-01-07 22:09:00Z

2

This should do the job

const input = ['GDAX', 'PLNX', 'BTRX']; // here you pass the strings that are given

const result = _.intersectionBy.apply(_, input.map(name => data[name]).concat(['pair']));

The input could also somehow automized, e.g. giving the object of true / false values for each name, so

const inputObject = { GDAX: true, PLNX: false, BTRX: true };

const names = ['GDAX', 'PLNX', 'BTRX'].filter(name => inputObject[name]);

const result = _.intersectionBy.apply(_, names.map(name => data[name]).concat(['pair']));

answered Jan 7, 2018 at 22:09

smnbbrv

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1 Comment

does_not_compute Over a year ago

Nice! That's exactly the kind of thing I was after, much appreciated i'll try hooking it up now

le_m · Accepted Answer · 2018-01-07 22:16:28Z

2

For readability and easy maintainability, I'd go with explicitly building a selection according to your boolean flags:

let selection = [];
if (GDAX) selection.push(data.GDAX);
if (PLNX) selection.push(data.PLNX);
if (BTRX) selection.push(data.BTRX);
const result = _.intersectionBy(...selection, 'pair');

answered Jan 7, 2018 at 22:16

le_m

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1 Comment

does_not_compute Over a year ago

Another cool answer thanks, forgot you can just spread arrays as arguements now as a neater way to .apply, thanks!

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