🪢 JavaScript

Comments in JSON

TL;DR: JSON is data-only. If you include a comment, then it must be data too.

{
    "//": "This is a comment",
    "key": "value"
}

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Conditional array/object content

const foo = [
    "bar",
    ...(truty ? ["baz"] : []),
    ...(falsy ? ["qux"] : []),
];

["bar", "baz"]

const foo = {
    bar: "bar",
    ...(truthy && { baz: 'baz' }),
    ...(falsy && { qux: 'qux' }),
};

{"bar": "bar", "baz": "baz"}

Map object entries

const mapObject = (obj, fn) => Object.fromEntries(Object.entries(obj).map(([k, v]) => [k, fn(v)]));

JSON stringify object values

mapObject({key: {foo: "bar"}}, (v) => JSON.stringify(v));

{key: '{"foo":"bar"}'}

Named capturing group regex

const semver = /^(?<major>\d+)(?:\.(?<minor>\d+)(?:\.(?<patch>\d+))?)?(?:-(?<label>.+))?$/;

const result = "1.2.3-alpha".match(semver);
result.groups.major; // '1'
result.groups.minor; // '2'
result.groups.patch; // '3'
result.groups.label; // 'alpha'

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Optional chaining operator

// The old way
val result = (obj || {}).data;
// The new way
val result = obj?.data;

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