JavaScript Snippet

Deep Merge Two Objects

Difficulty: Medium

Layering a defaults object under a user override is a daily need for config files, theme tokens, and React props, but `Object.assign` and spread only do shallow merges. This snippet walks from a recursive deep merge that follows nested plain objects, to an array-strategy variant that lets the caller pick concat vs replace, to a variadic version that folds an arbitrary number of layers from defaults to overrides.