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I have a Map like this:
const m = new Map(); m.set('key1', {}) . m.set('keyN' {}) the Mapcan have 1 or many items. Can I get the first item by index, without m.get('key1') and without a iterator loop?
like: m.get()[0]
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To get the first element of a Map , use destructuring assignment, e.g. const [firstKey] = map. keys() and const [firstValue] = map. values() . The keys() and values() methods return an iterator object that contains the Map's keys and values.
to get the first key in a map. So to set the first value, use the Map. prototype. set(); method using objects.
The Map object holds key-value pairs and remembers the original insertion order of the keys.
Iterate through a Map using JavaScript # Use the forEach() method to iterate over a Map object. The forEach method takes a function that gets invoked for each key/value pair in the Map , in insertion order. The function gets passed the value, key and the Map object on each iteration.
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', {} ]If you want to get the first key, then use Map.prototype.keys, like this
console.log(m.keys().next().value); // key1 Similarly if you want to get the first value, then you can use Map.prototype.values, like this
console.log(m.values().next().value); // {} 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.
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For the specific example you are wondering about, destructuring would be perfect.
let m = new Map(); m.set('key1', {}); m.set('key2', {}); let [[, obj]] = m; e.g.
let [pair] = m; let [key, obj] = pair; is one option to destructure and then grab the value, but the easier option would be
let [obj] = m.values(); If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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