sameish

A lightweight library for comparing JavaScript objects, designed with debugging in mind.

Including the following features:

• Pick specific fields to compare
• Ignore array order for specific fields
• Debug with human readable diff output
• Type safety when picking fields
• Works in browsers and on the server

Installation

npm install sameish

Usage

import { sameish } from "sameish";

Basic Comparison

const before = { name: "Alice", age: 30 };
const after = { age: 30, name: "Alice" };

sameish({ before, after }); // true

Compare Specific Paths

Compare only certain object paths using comparePaths:

const before = { user: { name: "Alice" }, meta: { updated: 1 } };
const after = { user: { name: "Alice" }, meta: { updated: 2 } };

sameish({
    before,
    after,
    comparePaths: ["user.name"],
}); // true (ignores meta.updated)

Ignore Array Order

Compare arrays without considering element order using ignoreOrderPaths:

const before = { tags: ["b", "a", "c"] };
const after = { tags: ["a", "b", "c"] };

sameish({
    before,
    after,
    ignoreOrderPaths: ["tags"],
}); // true

Debug with Diff Output

Enable logDiff to print differences:

sameish({
    before: { count: 1 },
    after: { count: 2 },
    logDiff: true,
}); // false

Logs the following to the console:

{
+   "count": 2,
-   "count": 1,
}

Use a custom log function:

sameish({
    before,
    after,
    logDiff: true,
    logFunction: (diff) => myLogger.debug(diff),
});

Optimize Bundle Size

If you are worried of bundle size in production, you can use the optimized version of sameish. E.g. in vite:

export default defineConfig(({ mode }) => ({
    resolve: {
        alias: mode === "production" ? { sameish: "sameish/optimized" } : {},
    },
}));

This will massively reduce the bundle size, since the human readable diff will not be bundled.

Here are the size differences:

| Import | Size | Gzipped | | :------------------ | -------: | -------: | | sameish | 48.77 kB | 14.08 kB | | sameish/optimized | 4.11 kB | 1.57 kB |