diff --git a/types/constant.d.ts b/types/constant.d.ts
new file mode 100644
index 0000000..9a80a45
--- /dev/null
+++ b/types/constant.d.ts
@@ -0,0 +1,30 @@
+/**
+ * Returns a function that always returns the supplied value.
+ *
+ * Useful for replacing an object outright rather than merging it.
+ *
+ * @memberOf u
+ *
+ * @example
+ * var alwaysFour = u.constant(4);
+ * expect(alwaysFour(32)).toEqual(4);
+ *
+ * @example
+ * var user = {
+ *   name: 'Mitch',
+ *   favorites: {
+ *     band: 'Nirvana',
+ *     movie: 'The Matrix'
+ *   }
+ * };
+ *
+ * var newFavorites = {
+ *   band: 'Coldplay'
+ * };
+ *
+ * var result = u({ favorites: u.constant(newFavorites) }, user);
+ *
+ * expect(result).toEqual({ name: 'Mitch', favorites: { band: 'Coldplay' } });
+ */
+export declare function constant<A>(value: A): (...args: any[]) => A;
+export default constant;
diff --git a/types/freeze.d.ts b/types/freeze.d.ts
new file mode 100644
index 0000000..e21475a
--- /dev/null
+++ b/types/freeze.d.ts
@@ -0,0 +1,12 @@
+/**
+ * Deeply freeze a plain javascript object.
+ *
+ * If `process.env.NODE_ENV === 'production'`, this returns the original object
+ * without freezing.
+ *
+ * Or if `process.env.UPDEEP_MODE === 'dangerously_never_freeze'`, this returns the original object
+ * without freezing.
+ *
+ */
+declare function freeze<O>(object: O): O;
+export default freeze;
diff --git a/types/if.d.ts b/types/if.d.ts
new file mode 100644
index 0000000..b1ba4bf
--- /dev/null
+++ b/types/if.d.ts
@@ -0,0 +1,13 @@
+import { Predicate, MergedUpdate, TruePredicate, FalsePredicate } from './types';
+export declare function uIf<TU, O>(predicate: FalsePredicate<O>, trueUpdates: TU, object: O): O;
+export declare function uIf<TU, O>(predicate: TruePredicate<O>, trueUpdates: TU, object: O): MergedUpdate<TU, O>;
+interface CurriedIf {
+    <TU, O>(predicate: TruePredicate<O>, trueUpdates: TU, object: O): MergedUpdate<TU, O>;
+    <TU, O>(predicate: FalsePredicate<O>, trueUpdates: TU, object: O): O;
+    <TU, O>(predicate: Predicate<O>, trueUpdates: TU, object: O): MergedUpdate<TU, O> | O;
+    <TU, O>(predicate: TruePredicate<O>, trueUpdates: TU): (object: O) => MergedUpdate<TU, O>;
+    <TU, O>(predicate: FalsePredicate<O>, trueUpdates: TU): (object: O) => O;
+    <TU, O>(predicate: Predicate<O>, trueUpdates: TU): (object: O) => MergedUpdate<TU, O> | O;
+}
+declare const _default: CurriedIf;
+export default _default;
diff --git a/types/ifElse.d.ts b/types/ifElse.d.ts
new file mode 100644
index 0000000..6eea6b1
--- /dev/null
+++ b/types/ifElse.d.ts
@@ -0,0 +1,13 @@
+import { Predicate, MergedUpdate, FalsePredicate, TruePredicate } from './types';
+export declare function updateIfElse<S, TU, FU>(predicate: TruePredicate<S>, trueUpdates: TU, falseUpdates: FU, object: S): MergedUpdate<TU, S>;
+export declare function updateIfElse<S, TU, FU>(predicate: FalsePredicate<S>, trueUpdates: TU, falseUpdates: FU, object: S): MergedUpdate<FU, S>;
+interface CurriedIfElse {
+    <S, TU, FU>(predicate: TruePredicate<S>, trueUpdates: TU, falseUpdates: FU, object: S): MergedUpdate<TU, S>;
+    <S, TU, FU>(predicate: FalsePredicate<S>, trueUpdates: TU, falseUpdates: FU, object: S): MergedUpdate<FU, S>;
+    <S, TU, FU>(predicate: Predicate<S>, trueUpdates: TU, falseUpdates: FU, object: S): MergedUpdate<TU, S> | MergedUpdate<FU, S>;
+    <S, TU, FU>(predicate: TruePredicate<S>, trueUpdates: TU, falseUpdates: FU): (object: S) => MergedUpdate<TU, S>;
+    <S, TU, FU>(predicate: FalsePredicate<S>, trueUpdates: TU, falseUpdates: FU): (object: S) => MergedUpdate<FU, S>;
+    <S, TU, FU>(predicate: Predicate<S>, trueUpdates: TU, falseUpdates: FU): (object: S) => MergedUpdate<TU, S> | MergedUpdate<FU, S>;
+}
+declare const _default: CurriedIfElse;
+export default _default;
diff --git a/types/index.d.ts b/types/index.d.ts
new file mode 100644
index 0000000..15a1c34
--- /dev/null
+++ b/types/index.d.ts
@@ -0,0 +1,30 @@
+import { constant } from './constant';
+import freeze from './freeze';
+import is from './is';
+import _if from './if';
+import ifElse from './ifElse';
+import map from './map';
+import omit from './omit';
+import omitBy from './omitBy';
+import reject from './reject';
+import update, { omitted } from './update';
+import updateIn from './updateIn';
+import withDefault from './withDefault';
+import { _ as placeholder } from './util/curry';
+declare const u: {
+    omit: typeof omit;
+    omitBy: typeof omitBy;
+    constant: typeof constant;
+    freeze: typeof freeze;
+    is: typeof is;
+    update: typeof update;
+    updateIn: typeof updateIn;
+    reject: typeof reject;
+    map: typeof map;
+    withDefault: typeof withDefault;
+    ifElse: typeof ifElse;
+    if: typeof _if;
+    omitted: typeof omitted;
+    _: typeof placeholder;
+} & typeof update;
+export default u;
diff --git a/types/is.d.ts b/types/is.d.ts
new file mode 100644
index 0000000..a3632c1
--- /dev/null
+++ b/types/is.d.ts
@@ -0,0 +1,9 @@
+import { Path } from './types';
+export declare function is(path: Path, predicate: any, object: any): boolean;
+interface CurriedIs {
+    (path: Path, predicate: any, object: any): boolean;
+    (path: Path, predicate: any): (object: any) => boolean;
+    (path: Path): (predicate: any) => (object: any) => boolean;
+}
+declare const _default: CurriedIs;
+export default _default;
diff --git a/types/map.d.ts b/types/map.d.ts
new file mode 100644
index 0000000..e8f1549
--- /dev/null
+++ b/types/map.d.ts
@@ -0,0 +1,11 @@
+import { MergedUpdate } from './types';
+declare type Mapped<I, O extends object> = {
+    [K in keyof O]: MergedUpdate<I, O[K]>;
+};
+export declare function map<I, O extends object>(iteratee: I, object: O): Mapped<I, O>;
+interface CurriedMap {
+    <I, O extends object>(iteratee: I, object: O): Mapped<I, O>;
+    <I, O extends object>(iteratee: I): (object: O) => Mapped<I, O>;
+}
+declare const _default: CurriedMap;
+export default _default;
diff --git a/types/omit.d.ts b/types/omit.d.ts
new file mode 100644
index 0000000..78bb67b
--- /dev/null
+++ b/types/omit.d.ts
@@ -0,0 +1,7 @@
+export declare function omit(predicate: string[] | string, collection: object): object;
+interface CurriedOmit {
+    (predicate: string[] | string, collection: object): object;
+    (predicate: string[] | string): (collection: object) => object;
+}
+declare const _default: CurriedOmit;
+export default _default;
diff --git a/types/omitBy.d.ts b/types/omitBy.d.ts
new file mode 100644
index 0000000..51e6cb8
--- /dev/null
+++ b/types/omitBy.d.ts
@@ -0,0 +1,7 @@
+export declare function omitBy<C extends object, P extends (...args: any[]) => boolean>(predicate: P, collection: C): object;
+interface CurriedOmitBy {
+    <C extends object, P extends (...args: any[]) => boolean>(predicate: P, collection: C): object;
+    <C extends object, P extends (...args: any[]) => boolean>(predicate: P): (collection: C) => object;
+}
+declare const _default: CurriedOmitBy;
+export default _default;
diff --git a/types/reject.d.ts b/types/reject.d.ts
new file mode 100644
index 0000000..2e7938c
--- /dev/null
+++ b/types/reject.d.ts
@@ -0,0 +1,9 @@
+export declare function reject<C extends object>(predicate: any, collection: C): C extends any[] ? C : object;
+interface CurriedReject {
+    <C extends any[]>(predicate: any, collection: C): C;
+    <C extends object>(predicate: any, collection: C): Array<C[keyof C]>;
+    <C extends any[]>(predicate: any): (collection: C) => C;
+    <C extends object>(predicate: any): (collection: C) => Array<C[keyof C]>;
+}
+declare const _default: CurriedReject;
+export default _default;
diff --git a/types/tests.ts b/types/tests.ts
new file mode 100644
index 0000000..2385a55
--- /dev/null
+++ b/types/tests.ts
@@ -0,0 +1,61 @@
+// TypeScript Version: 3.2.2
+import u from "updeep";
+
+u.omitted('whatever'); // $ExpectType { __omitted: boolean; }
+
+const obj = { this: 3 };
+
+u(true, obj); // $ExpectType true
+u(null, obj); // $ExpectType null
+u(undefined, obj); // $ExpectType undefined
+u("a specific string", obj); // $ExpectType "a specific string"
+
+u(true)(obj); // $ExpectType true
+u(null)(obj); // $ExpectType null
+u(undefined)(obj); // $ExpectType undefined
+u("a specific string")(obj); // $ExpectType "a specific string"
+
+const aString = "a" + "b";
+
+u(aString, obj); // $ExpectType string
+
+u((i: number) => "foo" + i, 1); // $ExpecType string
+u((i: number) => "foo" + i, "bar");
+
+// update is object
+u({ this: 2 }, true); // $ExpectType UpdateReturnMap<{ this: number; }>
+u({ this: 2 })(true); // $ExpectType UpdateReturnMap<{ this: number; }>
+
+u({ this: 2 }, { this: 3 }); // $ExpectType object
+u({ this: 2 })({ that: 3 }); // $ExpectType object
+
+u({ this: 2 })(true); // UpdateReturnMap<{ this: number; }>
+u({ this: 2 })({ that: 3 }); // $ExpectType object
+
+
+u.ifElse(false as boolean, { a: 1 }, { a: 2 }, { a: 3 }); // $ExpectType object
+u.ifElse(false as boolean, "foo", 3, { a: 3 }); // $ExpectType string | number
+u.ifElse(false, "foo", 3, { a: 3 }); // $ExpectType number
+u.ifElse(true, "foo", 3, { a: 3 }); // $ExpectType string
+
+// *** map ***
+const inc = (i:number) => i+1;
+
+u.map(inc, [1,2,3]); // $ExpectType number[]
+u.map(inc, ["potato"]); // $ExpectType number[]
+u.map({a:1},{a:2});  // $ExpectType Mapped<{ a: number; }, { a: number; }>
+
+u.omit('bar', { }); // $ExpectType object
+u.omit(['bar'], { }); // $ExpectType object
+
+u.omitBy([ 'banana' ], { } ); // $ExpectError
+
+// *** constant ***
+
+// $ExpectType { banana: number; }
+u.constant({ banana: 1 })('foo');
+
+/// *** freeze ***
+
+// $ExpectType { potato: number; }
+u.freeze({ potato: 1 });
diff --git a/types/tsconfig.json b/types/tsconfig.json
new file mode 100644
index 0000000..80ecf93
--- /dev/null
+++ b/types/tsconfig.json
@@ -0,0 +1,14 @@
+{
+    "compilerOptions": {
+        "module": "commonjs",
+        "lib": ["es6"],
+        "noImplicitAny": true,
+        "noImplicitThis": true,
+        "strictNullChecks": true,
+        "strictFunctionTypes": true,
+        "noEmit": true,
+
+        "baseUrl": "./",
+        "paths": { "updeep": ["."] }
+    }
+}
diff --git a/types/tslint.json b/types/tslint.json
new file mode 100644
index 0000000..c0c24d9
--- /dev/null
+++ b/types/tslint.json
@@ -0,0 +1,11 @@
+{
+    "extends": "dtslint/dtslint.json",
+    "rules": {
+        "trim-file": false,
+        "no-consecutive-blank-lines": false,
+        "typedef-whitespace": false,
+        "whitespace": false,
+        "space-within-parens": false,
+        "prefer-declare-function": false,
+        "no-unnecessary-generics": false,
+        "strict-export-declare-modifiers": false } }
diff --git a/types/types.d.ts b/types/types.d.ts
new file mode 100644
index 0000000..f0640af
--- /dev/null
+++ b/types/types.d.ts
@@ -0,0 +1,14 @@
+export declare type Updates = any;
+export declare type Source = any;
+export declare type PathPart = number | string;
+export declare type Path = PathPart | PathPart[];
+export declare type TruePredicate<S = any> = true | ((a: S) => true);
+export declare type FalsePredicate<S = any> = false | ((a: S) => false);
+export declare type Predicate<S = any> = boolean | ((arg: S) => boolean);
+export declare type MergedUpdate<U, O> = O extends object ? (UpdateReturnType<U> extends object ? object : UpdateReturnType<U>) : UpdateReturnType<U>;
+export declare type UpdateReturnMap<T> = {
+    [K in keyof T]: UpdateReturnType<T[K]>;
+};
+export declare type UpdateReturnType<U> = U extends (object: any) => any ? ReturnType<U> : U extends object ? UpdateReturnMap<U> : U;
+export declare type ReturningFunction = (...args: any[]) => any;
+export declare type ArgumentsType<F extends (...args: any[]) => any> = F extends (...args: infer A) => any ? A : never;
diff --git a/types/update.d.ts b/types/update.d.ts
new file mode 100644
index 0000000..7fe709a
--- /dev/null
+++ b/types/update.d.ts
@@ -0,0 +1,32 @@
+import { MergedUpdate, UpdateReturnType } from './types';
+export declare const omitted: (...args: any[]) => {
+    __omitted: boolean;
+};
+/**
+ * Recursively update an object or array.
+ *
+ * Can update with values:
+ * update({ foo: 3 }, { foo: 1, bar: 2 });
+ * // => { foo: 3, bar: 2 }
+ *
+ * Or with a function:
+ * update({ foo: x => (x + 1) }, { foo: 2 });
+ * // => { foo: 3 }
+ *
+ */
+export declare function update<U>(updates: U extends object ? never : U, object: any): U;
+export declare function update<U, O>(updates: U, object: O extends object ? never : O): UpdateReturnType<U>;
+export declare function update<U, O>(updates: U, object: O, ...args: any[]): MergedUpdate<U, O>;
+interface CurriedUpdate1<U> {
+    <O>(object: O extends object ? never : O): UpdateReturnType<U>;
+    <O>(object: O, ...args: any[]): MergedUpdate<U, O>;
+}
+interface CurriedUpdate {
+    <U>(updates: U extends object ? never : U, object: any): U;
+    <U, O>(updates: U, object: O extends object ? never : O): UpdateReturnType<U>;
+    <U, O>(updates: U, object: O, ...args: any[]): MergedUpdate<U, O>;
+    <U>(updates: U extends object ? never : U): (object: any) => U;
+    <U>(updates: U): CurriedUpdate1<U>;
+}
+declare const _default: CurriedUpdate;
+export default _default;
diff --git a/types/updateIn.d.ts b/types/updateIn.d.ts
new file mode 100644
index 0000000..62c3be1
--- /dev/null
+++ b/types/updateIn.d.ts
@@ -0,0 +1,12 @@
+import { Path } from './types';
+export declare function updateIn(path: Path, value: any, object: any): any;
+interface Curry2 {
+    (value: any, object: any): any;
+    (value: any): (object: any) => any;
+}
+interface CurriedUpdateIn {
+    (path: Path, value: any, object: any): any;
+    (path: Path): Curry2;
+}
+declare const _default: CurriedUpdateIn;
+export default _default;
diff --git a/types/util/curry.d.ts b/types/util/curry.d.ts
new file mode 100644
index 0000000..546b610
--- /dev/null
+++ b/types/util/curry.d.ts
@@ -0,0 +1,12 @@
+export declare const _ = "@@updeep/placeholder";
+interface SprawlingCurry<R, A extends any[]> {
+    (...args: A): R;
+    (): SprawlingCurry<R, A>;
+}
+export declare function curry1<R, A>(fn: (a: A) => R): SprawlingCurry<R, [A]>;
+export declare function curry1<R, A>(fn: (a: A, ...args: any) => R): SprawlingCurry<R, [A, ...any[]]>;
+export declare function curry2(fn: any): any;
+export declare function curry3(fn: any): any;
+export declare function curry4(fn: any): any;
+export default function curry(fn: (...args: any[]) => any, length?: 1 | 2 | 3 | 4): any;
+export {};
diff --git a/types/util/splitPath.d.ts b/types/util/splitPath.d.ts
new file mode 100644
index 0000000..94529e7
--- /dev/null
+++ b/types/util/splitPath.d.ts
@@ -0,0 +1,2 @@
+import { Path } from '../types';
+export default function splitPath(path: Path): Array<string | number>;
diff --git a/types/withDefault.d.ts b/types/withDefault.d.ts
new file mode 100644
index 0000000..c38c020
--- /dev/null
+++ b/types/withDefault.d.ts
@@ -0,0 +1,8 @@
+import { MergedUpdate } from './types';
+export declare function withDefault<D, U, O>(defaultValue: D, updates: U, object: O): MergedUpdate<U, O extends null | undefined ? D : O>;
+interface CurriedWithDefault {
+    <D, U, O extends any>(defaultValue: D, updates: U, object: O): MergedUpdate<U, O extends null | undefined ? D : O>;
+    <D, U>(defaultValue: D, updates: U): <O>(obj: O) => MergedUpdate<U, O extends null | undefined ? D : O>;
+}
+declare const _default: CurriedWithDefault;
+export default _default;
diff --git a/types/wrap.d.ts b/types/wrap.d.ts
new file mode 100644
index 0000000..955b2cf
--- /dev/null
+++ b/types/wrap.d.ts
@@ -0,0 +1,2 @@
+import { ReturningFunction } from './types';
+export default function wrap<F extends ReturningFunction, N extends number>(func: F, l?: N): any;