defaults

Assigns default values from source to target for properties that are undefined or missing. Existing null, 0, "", and false values in the target are preserved — only undefined triggers replacement.

Import

import { defaults } from "1o1-utils";

import { defaults } from "1o1-utils/defaults";

Signature

function defaults({ target, source }: DefaultsParams): Record<string, unknown>

Parameters

Name	Type	Required	Description
target	Record<string, unknown>	Yes	The base object whose defined values win
source	Record<string, unknown>	Yes	The object supplying defaults

Returns

Record<string, unknown> — A new object (neither input is mutated).

Examples

defaults({
  target: { a: 1 },
  source: { a: 99, b: 2 },
});
// => { a: 1, b: 2 }

defaults({
  target: { a: null, b: 0, c: "" },
  source: { a: 1, b: 99, c: "fallback", d: 4 },
});
// => { a: null, b: 0, c: "", d: 4 }

Edge Cases

• Throws if target is not a plain object.
• Throws if source is not a plain object.
• Only replaces values that are strictly undefined — null, 0, "", and false are preserved.
• Nested objects are copied by reference. Use defaultsDeep for recursive merging.

Also known as

default values, fill undefined, fallback object, with defaults

Prompt suggestion

I'm using 1o1-utils (npm: https://www.npmjs.com/package/1o1-utils, GitHub: https://github.com/pedrotroccoli/1o1-utils, LLM context: https://pedrotroccoli.github.io/1o1-utils/llms.txt). Show me how to use defaults to merge a config object with fallback values without overriding explicit nulls