An alternative to _.reduce for transforming objects and arrays: you mutate an accumulator in the iteratee. Return false to stop early. Part of Lodash 4.x Object (since 1.0.0).
Pass the object and path or keys shown below. Check whether the helper mutates or returns a new object.
Call _.transform. Start with this line.
_.transform(object, [iteratee], [accumulator])| Call | What it does |
|---|---|
_.transform(object, [iteratee], [accumulator]) | Primary signature. |
_.transform(object) | Work with an object’s keys, values, or paths. |
Prefer import transform from "lodash/transform" when you want a smaller bundle.
_.transform(object, [iteratee], [accumulator])| Parameter | Description |
|---|---|
| object | Required. Object or array to iterate |
| iteratee | Optional. (acc, value, key, collection) — mutate acc |
| accumulator | Optional. Seed result; defaults to a new empty object |
| Return Value | Description |
|---|---|
| * | The final accumulator |
Push squares until the iteratee returns false.
_.transform([2, 3, 4], function (result, n) {
result.push(n *= n);
return n % 2 === 0;
}, []);
// → [4, 9]n and push into result.false stops before 4.Build a lookup of values → list of keys.
_.transform({ a: 1, b: 2, c: 1 }, function (result, value, key) {
(result[value] || (result[value] = [])).push(key);
}, {});
// → { "1": ["a", "c"], "2": ["b"] }result[value] is an array.1 maps to a and c.Copy only keys that pass a condition — pickBy-style control.
_.transform({ a: 1, b: 2, c: 3 }, function (result, value, key) {
if (value > 1) {
result[key] = value;
}
}, {});
// → { b: 2, c: 3 }1.a: 1 is never written._.pickBy is shorter for simple predicates.Uppercase keys and double values in one pass.
_.transform({ a: 1, b: 2 }, function (result, value, key) {
result[key.toUpperCase()] = value * 2;
}, {});
// → { A: 2, B: 4 }key.toUpperCase().value * 2.transform vs reduceSame sum — different iteratee contracts.
_.transform([1, 2, 3], function (acc, n) {
acc.total += n;
}, { total: 0 });
// → { total: 6 }
_.reduce([1, 2, 3], function (acc, n) {
return acc + n;
}, 0);
// → 6acc.total in place.false._.transform is a Lodash Object helper (since 1.0.0). It runs anywhere Lodash runs — modern browsers (CDN or bundle) and Node.js / Bun / Deno with npm install lodash. Closest natives are Array.prototype.reduce / a manual for...in loop; Lodash adds a mutable-accumulator API and early exit via return false.
Available in [email protected] full builds and the lodash/transform modular import. Works in evergreen browsers and current Node LTS when Lodash is installed.
Bottom line: Safe for production once Lodash is loaded. Prefer import transform from "lodash/transform" for smaller builds. Ideal for one-pass map/filter/group builds with optional early exit.
Remove a nested property path from an object.
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