Lodash _.setWith() Method

What You’ll Learn

By the end of this tutorial, you’ll use _.setWith() to control how nested paths are built when plain _.set() is not enough.

What Is _.setWith()?

_.setWith() is like _.set() with an extra hook: a customizer function that decides what kind of container to create when Lodash needs a missing intermediate step along the path. The final value you pass is still assigned directly at the leaf—the customizer does not transform it.

Reach for it when you need explicit Array or Object constructors, custom container types, or fine-grained control over nested structure—especially for array-heavy paths like a[0].b.c.

📝 Syntax

The signature adds an optional fourth argument—the customizer:

_.setWith(object, path, value, [customizer])

Syntax Rules

• object — target object (mutated in place).
• path — same formats as _.set: dot string, brackets, or key array.
• value — assigned at the final path segment.
• customizer — optional (nsValue, key, object) => container; called when a missing intermediate container is needed.
• Return value — the same object reference.

import setWith from "lodash/setWith";

const object = {};
setWith(object, "a[0].b.c", 42, Object);

// object -> { a: [{ b: { c: 42 } }] }

Examples Gallery

Practical _.setWith() patterns with sample output and interactive Try It Yourself labs.

const object = {};

_.setWith(object, "a[0].b.c", 42, Object);

console.log(object);
// -> { a: [{ b: { c: 42 } }] }

{ a: [{ b: { c: 42 } }] }

const object = {};

_.setWith(object, "[0][1][2]", 3, Array);

console.log(object[0][1][2]);
// -> 3

Value at [0][1][2]: 3

const object = {};

const customizer = (nsValue, key) => {
  if (nsValue !== undefined) return nsValue;
  return String(+key) === key ? [] : {};
};

_.setWith(object, "rows[0].cells[1]", "Hello", customizer);

console.log(object.rows[0].cells[1]);
// -> "Hello"

rows[0].cells[1]: "Hello"

const object = { a: { b: { c: 42 } } };

_.setWith(object, "a.b.c", 99, Object);

console.log(object.a.b.c);
// -> 99

99

function createNested(path, value) {
  const object = {};
  _.setWith(object, path, value, Object);
  return object;
}

const nested = createNested("config.api.timeout", 5000);

console.log(nested);
// -> { config: { api: { timeout: 5000 } } }

{ config: { api: { timeout: 5000 } } }

const a = {};
const b = {};

_.set(a, "profile.name", "Ada");
_.setWith(b, "profile.name", "Ada", Object);

console.log(JSON.stringify(a) === JSON.stringify(b));
// -> true (same shape for simple object paths)

Both: { profile: { name: "Ada" } }

📝 Notes

• The customizer builds intermediate containers only—it does not transform the leaf value.
• Return undefined from the customizer to fall back to Lodash defaults (same as _.set).
• _.setWith mutates the target object like _.set.
• Passing Object or Array as the customizer is a common shorthand for container creation.
• For simple dot paths without special container rules, _.set() is usually enough.
• Do not confuse the setWith customizer with mergeWith merge rules—they solve different problems.

💡 Best Practices