diff --git a/.editorconfig b/.editorconfig
new file mode 100644
index 0000000..98a761d
--- /dev/null
+++ b/.editorconfig
@@ -0,0 +1,12 @@
+root = true
+
+[*]
+indent_style = tab
+end_of_line = lf
+charset = utf-8
+trim_trailing_whitespace = true
+insert_final_newline = true
+
+[{package.json,*.yml}]
+indent_style = space
+indent_size = 2
diff --git a/.gitattributes b/.gitattributes
new file mode 100644
index 0000000..176a458
--- /dev/null
+++ b/.gitattributes
@@ -0,0 +1 @@
+* text=auto
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..c9106a7
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+node_modules
+.nyc_output
diff --git a/.travis.yml b/.travis.yml
new file mode 100644
index 0000000..9f65308
--- /dev/null
+++ b/.travis.yml
@@ -0,0 +1,8 @@
+language: node_js
+node_js:
+  - '5'
+  - '4'
+  - '0.12'
+  - '0.10'
+after_script:
+  - npm run coveralls
diff --git a/index.js b/index.js
new file mode 100644
index 0000000..4afdf00
--- /dev/null
+++ b/index.js
@@ -0,0 +1,47 @@
+'use strict';
+var path = require('path');
+var AWS = require('aws-sdk');
+var Promise = require('pinkie-promise');
+var utils = require('./lib/utils');
+
+module.exports = function (name, alias, opts) {
+	if (typeof name !== 'string') {
+		return Promise.reject(new Error('Provide a AWS Lambda function name.'));
+	}
+
+	if (typeof alias !== 'string') {
+		return Promise.reject(new Error('Provide an alias name.'));
+	}
+
+	opts = opts || {};
+
+	// Load the credentials
+	AWS.config.region = opts.awsRegion || 'us-west-1';
+
+	if (opts.awsProfile) {
+		// Set the `credentials` property if a profile is provided
+		var objectCredentials = {
+			profile: opts.awsProfile
+		};
+
+		if (opts.awsFilename) {
+			objectCredentials.filename = path.resolve(process.cwd(), opts.awsFilename);
+		}
+
+		AWS.config.credentials = new AWS.SharedIniFileCredentials(objectCredentials);
+	}
+
+	// Create a lambda object
+	var lambda = new AWS.Lambda();
+
+	var options = {
+		FunctionName: name,
+		Name: alias
+	};
+
+	if (opts.version) {
+		options.FunctionVersion = opts.version;
+	}
+
+	return utils.updateOrCreate(lambda, options);
+};
diff --git a/lib/utils.js b/lib/utils.js
new file mode 100644
index 0000000..0a20f9c
--- /dev/null
+++ b/lib/utils.js
@@ -0,0 +1,50 @@
+'use strict';
+var pify = require('pify');
+var objectAssign = require('object-assign');
+var Promise = require('pinkie-promise');
+
+function findLatestVersion(lambda, opts) {
+	if (opts.FunctionVersion) {
+		// Return the function version if it was provided
+		return Promise.resolve(opts.FunctionVersion);
+	}
+
+	return pify(lambda.listVersionsByFunction.bind(lambda), Promise)({FunctionName: opts.FunctionName})
+		.then(function (data) {
+			if (!data.Versions || data.Versions.length === 0) {
+				throw new Error('No versions found.');
+			}
+
+			// Sort all the versions
+			data.Versions.sort(function (a, b) {
+				var aVersion = a.Version === '$LATEST' ? 0 : parseInt(a.Version, 10);
+				var bVersion = b.Version === '$LATEST' ? 0 : parseInt(b.Version, 10);
+
+				return bVersion - aVersion;
+			});
+
+			return data.Versions[0].Version;
+		});
+}
+
+function updateOrCreate(lambda, opts) {
+	var options = objectAssign({}, opts);
+
+	return findLatestVersion(lambda, opts)
+		.then(function (version) {
+			options.FunctionVersion = version;
+
+			// Try to update the version first
+			return pify(lambda.updateAlias.bind(lambda), Promise)(options);
+		})
+		.catch(function (err) {
+			if (err.code === 'ResourceNotFoundException') {
+				// If the alias does not exist yet, create it
+				return pify(lambda.createAlias.bind(lambda), Promise)(options);
+			}
+
+			throw err;
+		});
+}
+
+exports.updateOrCreate = updateOrCreate;
diff --git a/license b/license
new file mode 100644
index 0000000..78b0855
--- /dev/null
+++ b/license
@@ -0,0 +1,21 @@
+The MIT License (MIT)
+
+Copyright (c) Sam Verschueren <sam.verschueren@gmail.com> (github.com/SamVerschueren)
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
diff --git a/package.json b/package.json
new file mode 100644
index 0000000..c7cc7c5
--- /dev/null
+++ b/package.json
@@ -0,0 +1,43 @@
+{
+  "name": "lambda-update-alias",
+  "version": "0.0.0",
+  "description": "Update or create a AWS lambda alias",
+  "license": "MIT",
+  "repository": "SamVerschueren/lambda-update-alias",
+  "author": {
+    "name": "Sam Verschueren",
+    "email": "sam.verschueren@gmail.com",
+    "url": "github.com/SamVerschueren"
+  },
+  "engines": {
+    "node": ">=0.10.0"
+  },
+  "scripts": {
+    "test": "xo && nyc ava",
+    "coveralls": "nyc report --reporter=text-lcov | coveralls"
+  },
+  "files": [
+    "index.js",
+    "lib"
+  ],
+  "keywords": [
+    "aws",
+    "lambda",
+    "alias",
+    "update",
+    "create"
+  ],
+  "dependencies": {
+    "aws-sdk": "^2.3.0",
+    "object-assign": "^4.0.1",
+    "pify": "^2.3.0",
+    "pinkie-promise": "^2.0.0"
+  },
+  "devDependencies": {
+    "ava": "*",
+    "coveralls": "^2.11.9",
+    "nyc": "^6.1.1",
+    "sinon": "^1.17.3",
+    "xo": "*"
+  }
+}
diff --git a/readme.md b/readme.md
new file mode 100644
index 0000000..6c06d7a
--- /dev/null
+++ b/readme.md
@@ -0,0 +1,118 @@
+# lambda-update-alias
+
+[![Build Status](https://travis-ci.org/SamVerschueren/lambda-update-alias.svg?branch=master)](https://travis-ci.org/SamVerschueren/lambda-update-alias)
+[![Coverage Status](https://coveralls.io/repos/github/SamVerschueren/lambda-update-alias/badge.svg?branch=master)](https://coveralls.io/github/SamVerschueren/lambda-update-alias?branch=master)
+
+> Update or create a AWS lambda alias
+
+
+## Install
+
+```
+$ npm install --save lambda-update-alias
+```
+
+
+## Usage
+
+```js
+const updateAlias = require('lambda-update-alias');
+
+updateAlias('myLambdaFunction', 'v1'}).then(result => {
+	console.log(result);
+	/*
+	{
+		AliasArn: 'arn:aws:lambda:us-west-1:123456789012:function:myLambdaFunction:v1',
+		Name: 'v1',
+		FunctionVersion: '3',
+		Description: 'My lambda function description'
+	}
+	*/
+});
+```
+
+
+## API
+
+### updateAlias(name, alias, [options])
+
+Returns a promise for the result object.
+
+#### name
+
+Type: `string`
+
+Name of the lambda function.
+
+#### alias
+
+Type: `string`
+
+Name of the alias that should be attached to the lambda function.
+
+#### options
+
+##### version
+
+Type: `string`<br>
+Default: *`latest`*
+
+Name of the version where the alias should be attached to. If not provided, the alias will be attached to the version
+with the highest number. `$LATEST` is treated as version `0`.
+
+##### awsProfile
+
+Type: `string`
+
+[AWS Profile](http://docs.aws.amazon.com/AWSJavaScriptSDK/guide/node-configuring.html). The user related to the profile should have
+admin access to API Gateway and should be able to invoke `lambda:AddPermission`.
+
+Can be overridden globally with the `AWS_PROFILE` environment variable.
+
+##### awsFilename
+
+Type: `string`
+
+[Filename](http://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/SharedIniFileCredentials.html#constructor-property) to use when loading credentials.
+
+##### awsRegion
+
+Type: `string`<br>
+Default: `us-west-1`
+
+AWS region.
+
+
+## User Policy
+
+The profile creating or updating the alias should be able to list the versions of the function and create and update the aliases.
+
+```json
+{
+    "Version": "2012-10-17",
+    "Statement": [
+        {
+            "Sid": "Stmt1454507191000",
+            "Effect": "Allow",
+            "Action": [
+                "lambda:CreateAlias",
+                "lambda:ListVersionsByFunction",
+                "lambda:UpdateAlias"
+            ],
+            "Resource": [
+                "*"
+            ]
+        }
+    ]
+}
+```
+
+
+## Related
+
+- [lambda-update-alias-cli](https://github.com/SamVerschueren/lambda-update-alias-cli) - CLI for this module
+
+
+## License
+
+MIT © [Sam Verschueren](https://github.com/SamVerschueren)
diff --git a/test/fixtures/aws.js b/test/fixtures/aws.js
new file mode 100644
index 0000000..93209f2
--- /dev/null
+++ b/test/fixtures/aws.js
@@ -0,0 +1,13 @@
+'use strict';
+var AWS = require('aws-sdk');
+
+var lambda = new AWS.Lambda();
+
+AWS.Lambda = function () {
+	return lambda;
+};
+
+module.exports = {
+	lambda: lambda,
+	config: AWS.config
+};
diff --git a/test/test.js b/test/test.js
new file mode 100644
index 0000000..2600ea6
--- /dev/null
+++ b/test/test.js
@@ -0,0 +1,55 @@
+import path from 'path';
+import test from 'ava';
+import sinon from 'sinon';
+import aws from './fixtures/aws';
+import utils from '../lib/utils';
+import m from '../';
+
+test.before(() => {
+	sinon.stub(utils, 'updateOrCreate');
+});
+
+test('throw error if no lambda function name is provided', t => {
+	t.throws(m(), 'Provide a AWS Lambda function name.');
+});
+
+test('throw error if no alias name is provided', t => {
+	t.throws(m('foo'), 'Provide an alias name.');
+});
+
+test('specify the aws profile', async t => {
+	await m('foo', 'v1', {awsProfile: 'foo-profile'});
+	t.is(aws.config.credentials.profile, 'foo-profile');
+});
+
+test('specify the aws filename', async t => {
+	await m('foo', 'v1', {awsProfile: 'foo-profile', awsFilename: './credentials'});
+	t.is(aws.config.credentials.filename, path.resolve(process.cwd(), 'credentials'));
+});
+
+test.serial('use `us-west-1` as default region', async t => {
+	await m('foo', 'v1');
+	t.is(aws.config.region, 'us-west-1');
+});
+
+test.serial('provide region property', async t => {
+	await m('foo', 'v1', {awsRegion: 'eu-west-1'});
+	t.is(aws.config.region, 'eu-west-1');
+});
+
+test.serial('update or create the alias', async t => {
+	await m('foo', 'v1');
+	t.same(utils.updateOrCreate.lastCall.args[1], {
+		FunctionName: 'foo',
+		Name: 'v1'
+	});
+});
+
+test.serial('update or create the alias on a specific version', async t => {
+	await m('foo', 'v1', {version: '1'});
+	t.same(utils.updateOrCreate.lastCall.args[1], {
+		FunctionName: 'foo',
+		FunctionVersion: '1',
+		Name: 'v1'
+	});
+});
diff --git a/test/utils.js b/test/utils.js
new file mode 100644
index 0000000..f892779
--- /dev/null
+++ b/test/utils.js
@@ -0,0 +1,78 @@
+import test from 'ava';
+import sinon from 'sinon';
+import {updateOrCreate} from '../lib/utils';
+
+const resourceNotFoundException = new Error('Resource not found');
+resourceNotFoundException.code = 'ResourceNotFoundException';
+
+const fooVersions = {
+	Versions: [
+		{Version: '$LATEST'},
+		{Version: '1'},
+		{Version: '2'}
+	]
+};
+
+const barVersions = {
+	Versions: [
+		{Version: '$LATEST'}
+	]
+};
+
+test.beforeEach(t => {
+	const listVersionsStub = sinon.stub();
+	listVersionsStub.withArgs({FunctionName: 'foo'}).yields(undefined, fooVersions);
+	listVersionsStub.withArgs({FunctionName: 'bar'}).yields(undefined, barVersions);
+	listVersionsStub.withArgs({FunctionName: 'baz'}).yields(undefined, {Versions: []});
+	listVersionsStub.withArgs({FunctionName: 'bax'}).yields(undefined, {});
+
+	const updateAliasStub = sinon.stub();
+	updateAliasStub.withArgs({FunctionName: 'foo', FunctionVersion: '2'}).yields(undefined, {foo: 'bar'});
+	updateAliasStub.yields(resourceNotFoundException);
+
+	const createAliasStub = sinon.stub();
+	createAliasStub.yields(undefined, {foo: 'bar'});
+
+	const lambda = {};
+	lambda.listVersionsByFunction = listVersionsStub;
+	lambda.updateAlias = updateAliasStub;
+	lambda.createAlias = createAliasStub;
+
+	t.context.lambda = lambda;
+});
+
+test('`listVersionsByFunction` should be called if no `version` is provided', async t => {
+	const lambda = t.context.lambda;
+	await updateOrCreate(lambda, {FunctionName: 'foo'});
+	t.same(lambda.listVersionsByFunction.args[0][0], {FunctionName: 'foo'});
+});
+
+test('`listVersionsByFunction` should not be called if `version` is provided', async t => {
+	const lambda = t.context.lambda;
+	await updateOrCreate(lambda, {FunctionName: 'foo', FunctionVersion: '1'});
+	t.true(lambda.listVersionsByFunction.callCount === 0);
+});
+
+test('error if no versions could be found', t => {
+	const lambda = t.context.lambda;
+	t.throws(updateOrCreate(lambda, {FunctionName: 'baz'}), 'No versions found.');
+	t.throws(updateOrCreate(lambda, {FunctionName: 'bax'}), 'No versions found.');
+});
+
+test('`updateAlias` should be called', async t => {
+	const lambda = t.context.lambda;
+	await updateOrCreate(lambda, {FunctionName: 'foo'});
+	t.same(lambda.updateAlias.args[0][0], {
+		FunctionName: 'foo',
+		FunctionVersion: '2'
+	});
+});
+
+test('`createAlias` if alias does not exist', async t => {
+	const lambda = t.context.lambda;
+	await updateOrCreate(lambda, {FunctionName: 'bar'});
+	t.same(lambda.createAlias.args[0][0], {
+		FunctionName: 'bar',
+		FunctionVersion: '$LATEST'
+	});
+});