ecmascript-6

First item from a Map on JavaScript ES2015

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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); // … Read more

Keyword ‘const’ does not make the value immutable. What does it mean?

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When you make something const in JavaScript, you can’t reassign the variable itself to reference something else. However, the variable can still reference a mutable object. const x = {a: 123}; // This is not allowed. This would reassign `x` itself to refer to a // different object. x = {b: 456}; // This, however, … Read more