Iterates over an object’s own and inherited enumerable string keys, calling the iteratee for each. Closer to native for…in than to Object.keys. Since Lodash 0.3.0.
Pass the object and path or keys shown below. Check whether the helper mutates or returns a new object.
Call _.forIn. Start with this line.
_.forIn(object, [iteratee=_.identity])| Call | What it does |
|---|---|
_.forIn(object, [iteratee=_.identity]) | Primary signature. |
_.forIn(object) | Work with an object’s keys, values, or paths. |
Prefer import forIn from "lodash/forIn" when you want a smaller bundle.
_.forIn(object, [iteratee=_.identity])| Parameter | Description |
|---|---|
| object | Required. Object to iterate (returned unchanged) |
| iteratee | Optional. Defaults to _.identity |
| Return Value | Description |
|---|---|
| * | The original object |
Prototype enumerable keys are visited too.
function Foo() {
this.a = 1;
this.b = 2;
}
Foo.prototype.c = 3;
var keys = [];
_.forIn(new Foo(), function (value, key) {
keys.push(key);
});
// → ["a", "b", "c"]a and b.c.(value, key, object) each time._.forOwnforOwn skips the prototype; forIn includes it.
var obj = new Foo();
var withIn = [];
var withOwn = [];
_.forIn(obj, function (v, k) { withIn.push(k); });
_.forOwn(obj, function (v, k) { withOwn.push(k); });
// withIn → ["a", "b", "c"]
// withOwn → ["a", "b"]c.c.falseReturn false to stop as soon as you find what you need.
var seen = [];
_.forIn({ a: 1, b: 2, c: 3 }, function (value, key) {
seen.push(key);
if (key === "b") return false;
});
// seen → ["a", "b"]false.false stops; other falsy returns do not._.forIn returns the original object — handy for chaining side effects.
var source = { x: 10, y: 20 };
var pairs = [];
var same = _.forIn(source, function (value, key) {
pairs.push(key + "=" + value);
});
same === source; // true
// pairs → ["x=10", "y=20"]source, not a new array._.mapValues / _.transform to build results._.forInRightSame keys; opposite walk order.
var left = [];
var right = [];
var data = { a: 1, b: 2, c: 3 };
_.forIn(data, function (v, k) { left.push(k); });
_.forInRight(data, function (v, k) { right.push(k); });
// left → ["a", "b", "c"]
// right → ["c", "b", "a"]_.forIn is a Lodash Object helper (since 0.3.0). It runs anywhere Lodash 4.x runs — modern browsers (CDN or bundle) and Node.js / Bun / Deno with npm install lodash.
Available in [email protected] full builds and the lodash/forIn 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 forIn from "lodash/forIn". Use forOwn when inherited keys should be ignored.
Iterate own and inherited enumerable keys in reverse order.
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