projects.js

import { computed, observable, action } from 'mobx'

class Projects {
  @observable projects = []
  
  constructor (projects) {
    this.projects = projects
  }

  removeProject (projectId) {
    // this removes ALL projects
    this.projects = _.filter(this.projects, (project) => {
      !(project.id === projectId)
    })
  }
  
  removeProject (projectId) {
    // this removes 1 project
    this.projects = _.filter(this.projects, (project) => !(project.id === projectId))
  }
}

projects = new Projects([{id: '123', path: 'foo'}, {id: '456', path: 'bar'}])
projects.removeProject('123')