Get all keys from a Map() according to their property value in Javascript

Question

I am currently trying to get all keys from a Map() structure in JS/TS which met a specific criteria, so I am able to change a value of another property of the same elements:

const map1 = new Map(); map1.set('a', {price:1, stock:true}); map1.set('b', {price:3, stock:false}); map1.set('c', {price:5, stock:true});

How can I get to know, for example, all keys where price > 1? The output could be an array of anything else that can be used to handle the map and change its properties according to the respective constraint. In case I would like to change all 'stock' properties to false when price > 1.

Thanks!

please specify a single result. do you want to update the map or get an array of objects? — Nina Scholz
– Nina Scholz, Commented Aug 29, 2022 at 21:45
I actually want to update the map specific property if the condition is met. I've just mentioned the array example since I imagine that one alternative would be to handle an array from it. However, the objective is to update the map indeed. — NemesiS
– NemesiS, Commented Aug 29, 2022 at 22:15

Konrad · Accepted Answer · 2022-08-29 21:40:57Z

[...map1].filter should do

const map1 = new Map(); map1.set('a', {price:1, stock:true}); map1.set('b', {price:3, stock:false}); map1.set('c', {price:5, stock:true}); const map2 = new Map([ ...map1 ].filter(([key, value]) => value.price > 3)) console.log([...map2])

This could be one approach indeed. However, looks like it returns an array which would require some additional iterations to allow to modify the Map properties.

Nina Scholz · Accepted Answer · 2022-08-30 08:00:36Z

You could iterate the map directly and apply update if necessary.

const map1 = new Map([['a', { price: 1, stock: true }], ['b', { price: 3, stock: false }], ['c', { price: 5, stock: true }]]); map1.forEach(value => { if (value.price > 1) value.stock = false; }); console.log([...map1]);

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