environment works as you might expect.

---
### A playbook demonstrating a common npm workflow:
# - Check for package.json in the application directory
# - If package.json exists:
#   * Run npm prune
#   * Run npm install

- hosts: application
  become: false

  vars:
    node_app_dir: /var/local/my_node_app

  environment:
    NVM_DIR: /var/local/nvm
    PATH: /var/local/nvm/versions/node/v4.2.1/bin:{{ ansible_env.PATH }}

  tasks:
  - name: check for package.json
    stat:
      path: '{{ node_app_dir }}/package.json'
    register: packagejson

  - name: npm prune
    command: npm prune
    args:
      chdir: '{{ node_app_dir }}'
    when: packagejson.stat.exists

  - name: npm install
    npm:
      path: '{{ node_app_dir }}'
    when: packagejson.stat.exists

Sources

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