deepMerge

deepMerge(obj1, obj2) → object · Object

Recursively merge two objects. At each level, properties from obj2 override obj1. Nested objects are merged recursively (not replaced).

• obj1 (required): base object

• obj2 (required): override object

let base = {server: {host: "localhost", port: 5432, ssl: false}}
let prod = {server: {host: "prod-db.example.com", ssl: true}}
{
  config: deepMerge(base, prod)
}
// Output: {config: {server: {host: "prod-db.example.com", port: 5432, ssl: true}}}
// port survived from base — deep merge, not replace

Contrast with spread: {...base, ...prod} would REPLACE the entire server object, losing port. deepMerge preserves nested properties.