First item from a Map on JavaScript ES2015

Question

I have a Map like this:

const m = new Map();
m.set(\'key1\', {})
.
m.set(\'keyN\' {})

the Mapcan have 1 or many i

Answer 1

Use the Map.prototype.entries function, like this

const m = new Map();
m.set('key1', {})
m.set('keyN', {})

console.log(m.entries().next().value); // [ 'key1', {} ]

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If you want to get the first key, then use Map.prototype.keys, like this

console.log(m.keys().next().value); // key1

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Similarly if you want to get the first value, then you can use Map.prototype.values, like this

console.log(m.values().next().value); // {}

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The reason why we have to call next() on the returned values is that, all those functions return iterators. Read more about the iteration protocol here.