So-called object-path notation

Book Node.js Design Patterns, 3rd edition Nearly a decade ago, Mario Casciaro, the author of Node.js Design Patternsopens in a new tab book, published an npm package object-pathopens in a new tab.

It’s a getter/setter helper which works on any data structures:

import { get } from "object-path";
const testObj1 = {
  foo: {
    bar: "value",
  },
};
const testObj2 = {};

console.log(get(testObj1, "foo.bar"));
// => "value"

console.log(get(testObj2, "foo.bar"));
// => null

The optional chainingopens in a new tab is a substitute for get (provided you put question marks correct in front of every dot), but there are eight more methods in object-path which don’t have native JS equivalents.

But object-path has one peculiar detail — it marks the array paths also using dots, not brackets (as in native JS):

import { get } from "object-path";
const testArr1 = [["value"]];
const testArr2 = [];

console.log(get(testArr1, "0.0"));
// => "value"

console.log(get(testArr2, "0.0"));
// => null

Practically, this dot-based path notation makes the life easier, both for program authors and program users. Just compare somePath.split(".").some(...) with… ahem, whatever the bracket-aware equivalent would be…

When objects and arrays are nested, we get paths like foo.1.bar.3.value (as opposed to native JS foo[1].bar[3].value).

Many packages our ours use this “dot notation”: