CODEWITHSUNDEEP
javascriptecmascript-6
Tim Givois
Tim Givois

Reputation: 2014

Ecmascript 6 Map filter

What is the best way to filter data in a Map by value?

I have implemented the forEach and then added the key-values to another Map (as it is not recommended to delete the map while iterating)

theMap.forEach((value, key) => { if (value !== 'something') { otherMap.set(key, value)}})

Is there any more efficient way to filter the Map by value? I tried using lodash filter function but couldn't implement it...

Upvotes: 0

Views: 106

Answers (2)

loretoparisi
loretoparisi

Reputation: 16281

I would do like

var m = new Map()
m.set("a", {x: 1})
m.set("b", {x: 2})
m.set("c", {x: 3})
var f = new Map([...m].filter(v => v[1].x >= 3))

where of course you can change the filter depending of your map values type

Upvotes: 0

loganfsmyth
loganfsmyth

Reputation: 161457

Probably easiest would be to create a temporary array while iterating, like

Array.from(theMap).forEach(([key, value]) => {
  if (someFilterLogic) theMap.delete(key);
});

or create a new Map instead, e.g.

theMap = new Map(Array.from(theMap).filter(([key, value]) => someFilterLogic));

Generally worrying about "efficient" with JS code is best left to a profiler. What counts as efficient varies massively between browsers and versions. Unless you've profiled and explicitly know something is a bottleneck, or have written your code with a truly incorrect algorithmic runtime, don't worry about it.

Upvotes: 3

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