How to Filter Entries in a JavaScript Map

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#1

How can you filter entries in a JavaScript Map?

#2

One way to filter entries in a javascript map filter is to use the for...of loop. This method is straightforward: it iterates through each entry and filters them based on a condition. Here’s an example:

const map = new Map([['a', 1], ['b', 2], ['c', 3]]);
const filteredMap = new Map();

for (const [key, value] of map) {
    if (value > 1) {
        filteredMap.set(key, value);
    }
}

console.log(filteredMap); // Map { 'b' => 2, 'c' => 3 }

This approach directly uses a loop, which makes it flexible if you want to add extra conditions or operations.

#3

Building on what Yanisleidi shared, another efficient way to filter a javascript map filter is by using Array.from() with filter(). With Array.from(), you can convert the Map to an array, apply filter() to each entry, and then recreate a Map. This approach can be more concise:

const map = new Map([['a', 1], ['b', 2], ['c', 3]]);
const filteredMap = new Map(
    Array.from(map).filter(([key, value]) => value > 1)
);

console.log(filteredMap); // Map { 'b' => 2, 'c' => 3 }

This technique combines readability with the power of filter(), making it an efficient choice when working with javascript map filter operations in one line.

#4

I like Ambika’s Array.from() suggestion! Another method worth mentioning is using map.forEach() for filtering directly. With this approach, you can access each Map entry, and it’s especially handy if you want to perform extra actions while filtering. Here’s how it works:

const map = new Map([['a', 1], ['b', 2], ['c', 3]]);
const filteredMap = new Map();

map.forEach((value, key) => {
    if (value > 1) {
        filteredMap.set(key, value);
    }
});

console.log(filteredMap); // Map { 'b' => 2, 'c' => 3 }

Using forEach() keeps the syntax simple and functional, which is great for chaining operations on each entry during a javascript map filter.