diff --git a/.eslintrc.js b/.eslintrc.js
new file mode 100644
index 0000000..1398317
--- /dev/null
+++ b/.eslintrc.js
@@ -0,0 +1,43 @@
+module.exports = {
+  "root": true,
+  "extends": "eslint:recommended",
+  "env": {
+    "node": true,
+    "es6": true,
+    "amd": true,
+    "browser": true
+  },
+  "parserOptions": {
+    "ecmaFeatures": {
+      "globalReturn": true,
+      "generators": false,
+      "objectLiteralDuplicateProperties": false,
+      "experimentalObjectRestSpread": true
+    },
+    "ecmaVersion": 2017,
+    "sourceType": "module"
+  },
+  "plugins": [
+    "import"
+  ],
+  "settings": {
+    "import/core-modules": [],
+    "import/ignore": [
+      "node_modules",
+      "\\.(coffee|scss|css|less|hbs|svg|json)$"
+    ]
+  },
+  "rules": {
+    "no-console": 0,
+    "comma-dangle": [
+      "error",
+      {
+        "arrays": "always-multiline",
+        "objects": "always-multiline",
+        "imports": "always-multiline",
+        "exports": "always-multiline",
+        "functions": "ignore"
+      }
+    ]
+  }
+}
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..3c3629e
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+node_modules
diff --git a/README.md b/README.md
index a6b272b..46251e6 100644
--- a/README.md
+++ b/README.md
@@ -1,2 +1,25 @@
-# cocoon-vanilla-js
+# cocoon-vanilla-js (private)
+
 A vanilla JS replacement for (Rails) Cocoon's jQuery script
+
+
+## Usage
+
+Replace `<token>` and `<commit>` with the corresponding values:
+
+```
+yarn add git+https://<token>:x-oauth-basic@github.com/kollegorna/cocoon-vanilla-js.git#<commit>
+```
+
+Import as ES6 module:
+
+```js
+import 'cocoon-vanilla-js'
+```
+
+## Notes
+
+To broaden browser support, use the following polyfills:
+
+- [Element.closest](https://www.npmjs.com/package/element-closest)
+- [Element.classList](https://www.npmjs.com/package/classlist-polyfill)
diff --git a/index.js b/index.js
new file mode 100644
index 0000000..bae19f7
--- /dev/null
+++ b/index.js
@@ -0,0 +1,162 @@
+let cocoon_element_counter = 0;
+
+const create_new_id = function() {
+  return (new Date().getTime() + cocoon_element_counter++);
+};
+
+const newcontent_braced = function(id) {
+  return '[' + id + ']$1';
+};
+
+const newcontent_underscord = function(id) {
+  return '_' + id + '_$1';
+};
+
+const getInsertionNodeElem = function(insertionNode, insertionTraversal, btn) {
+  if(!insertionNode){
+    return btn.parentNode;
+  }
+  else { // string
+    if(insertionTraversal) {
+      // TODO:
+      // https://github.com/nathanvda/cocoon/blob/master/app/assets/javascripts/cocoon.js#L32
+      // data-association-insertion-traversal: the jquery traversal method to
+      // allow node selection relative to the link. closest, next, children, etc.
+      // return $this[insertionTraversal](insertionNode);
+      return null;
+    }
+    else {
+      return document.querySelector(insertionNode);
+    }
+  }
+};
+
+const addFieldsHandler = (btn) => {
+  const assoc = btn.getAttribute('data-association');
+  const assocs = btn.getAttribute('data-associations');
+  const content = btn.getAttribute('data-association-insertion-template');
+  const insertionNode = btn.getAttribute('data-association-insertion-node');
+  const insertionTraversal = btn.getAttribute('data-association-insertion-traversal');
+  let insertionMethod = btn.getAttribute('data-association-insertion-method') || btn.getAttribute('data-association-insertion-position') || 'before';
+  let new_id = create_new_id();
+  let count = parseInt(btn.getAttribute('data-count'), 10);
+  let regexp_braced = new RegExp('\\[new_' + assoc + '\\](.*?\\s)', 'g');
+  let regexp_underscord = new RegExp('_new_' + assoc + '_(\\w*)', 'g');
+  let new_content = content.replace(regexp_braced, newcontent_braced(new_id));
+  let new_contents = [];
+
+  if(new_content == content) {
+    regexp_braced = new RegExp('\\[new_' + assocs + '\\](.*?\\s)', 'g');
+    regexp_underscord = new RegExp('_new_' + assocs + '_(\\w*)', 'g');
+    new_content = content.replace(regexp_braced, newcontent_braced(new_id));
+  }
+
+  new_content = new_content.replace(regexp_underscord, newcontent_underscord(new_id));
+  new_contents = [new_content];
+
+  count = (isNaN(count) ? 1 : Math.max(count, 1));
+  count -= 1;
+
+  while(count) {
+    new_id = create_new_id();
+    new_content = content.replace(regexp_braced, newcontent_braced(new_id));
+    new_content = new_content.replace(regexp_underscord, newcontent_underscord(new_id));
+    new_contents.push(new_content);
+    count -= 1;
+  }
+
+  const insertionNodeElem = getInsertionNodeElem(insertionNode, insertionTraversal, btn);
+
+  if(!insertionNodeElem || (insertionNodeElem.length == 0)) {
+    console.warn("Couldn't find the element to insert the template. Make sure your `data-association-insertion-*` on `link_to_add_association` is correct.");
+  }
+
+  new_contents.forEach((node) => {
+    const event = new CustomEvent('cocoon:before-insert', {detail: node});
+    insertionNodeElem.dispatchEvent(event);
+
+    if(!event.defaultPrevented) {
+      switch(insertionMethod) {
+        default:
+        case 'before':
+          insertionMethod = 'beforebegin';
+        break;
+        case 'after':
+          insertionMethod = 'afterend';
+        break;
+        case 'append':
+          insertionMethod = 'beforeend';
+        break;
+        case 'prepend':
+          insertionMethod = 'afterbegin';
+        break;
+      }
+
+      insertionNodeElem.insertAdjacentHTML(insertionMethod, node);
+      insertionNodeElem.dispatchEvent(
+        CustomEvent('cocoon:before-insert', {detail: node})
+      );
+    }
+  });
+};
+
+document.addEventListener('click', (e) => {
+  if(e.target.matches('.add_fields')) {
+    e.preventDefault();
+    e.stopPropagation();
+    addFieldsHandler(e.target);
+  }
+});
+
+const removeFieldsHandler = (btn) => {
+  const wrapperClass = btn.getAttribute('data-wrapper-class') || 'nested-fields';
+  const nodeToDelete = btn.closest(`.${wrapperClass}`);
+  const triggerNode = nodeToDelete.parentNode;
+
+  const event = new CustomEvent('cocoon:before-remove', {detail: nodeToDelete});
+  triggerNode.dispatchEvent(event);
+
+  if(!event.defaultPrevented) {
+    const timeout = triggerNode.getAttribute('data-remove-timeout') || 0;
+
+    setTimeout(() => {
+      if(btn.classList.contains('dynamic')) {
+        // nodeToDelete.remove();
+        nodeToDelete.parentNode.removeChild(nodeToDelete);
+      }
+      else {
+        const input = btn.previousElementSibling;
+        if(input && input.matches('input[type=hidden]')) {
+          input.value = 1;
+        }
+        nodeToDelete.style.display = 'none';
+      }
+
+      triggerNode.dispatchEvent(
+        CustomEvent('cocoon:after-remove', {detail: nodeToDelete})
+      );
+    }, timeout);
+  }
+};
+
+document.addEventListener('click', (e) => {
+  if(
+    e.target.matches('.remove_fields.dynamic') ||
+    e.target.matches('.remove_fields.existing')
+  ) {
+    e.preventDefault();
+    e.stopPropagation();
+    removeFieldsHandler(e.target);
+  }
+});
+
+const hideFields = () => {
+  [...document.querySelectorAll('.remove_fields.existing.destroyed')].forEach((btn) => {
+    const wrapperClass = btn.getAttribute('data-wrapper-class') || 'nested-fields';
+    btn.closest(`.${wrapperClass}`).style.display = 'none';
+  });
+};
+
+document.addEventListener('DOMContentLoaded', hideFields);
+document.addEventListener('turbolinks:load', hideFields);
+document.addEventListener('page:load', hideFields);
diff --git a/package.json b/package.json
new file mode 100644
index 0000000..f3725f2
--- /dev/null
+++ b/package.json
@@ -0,0 +1,19 @@
+{
+  "name": "cocoon-vanilla-js",
+  "version": "1.0.0",
+  "description": "A vanilla JS replacement for (Rails) Cocoon's jQuery script",
+  "main": "index.js",
+  "engines": {
+    "node": "<=9.11.2"
+  },
+  "repository": "git+https://github.com/kollegorna/cocoon-vanilla-js.git",
+  "author": "Kollegorna",
+  "license": "MIT",
+  "bugs": {
+    "url": "https://github.com/kollegorna/cocoon-vanilla-js/issues"
+  },
+  "homepage": "https://github.com/kollegorna/cocoon-vanilla-js#readme",
+  "devDependencies": {},
+  "dependencies": {},
+  "private": true
+}
diff --git a/yarn.lock b/yarn.lock
new file mode 100644
index 0000000..67ea6d5
--- /dev/null
+++ b/yarn.lock
@@ -0,0 +1,7 @@
+# THIS IS AN AUTOGENERATED FILE. DO NOT EDIT THIS FILE DIRECTLY.
+# yarn lockfile v1
+
+
+"js-utils@git+https://8265015e18616ae2d58e38f4fd9ca111b8beaff8:x-oauth-basic@github.com/kollegorna/js-utils.git#6507589":
+  version "1.0.0"
+  resolved "git+https://8265015e18616ae2d58e38f4fd9ca111b8beaff8:x-oauth-basic@github.com/kollegorna/js-utils.git#6507589ae81c91ff2db72d7c4905a3d2d52674f9"