Changing state of array object - reactjs

Question

I have the following state:

this.state = {
 teams: [ 
  {'name': 'Team1', teamMembers: ['adam', 'jack'] },
  {'name': 'Team2', teamMembers: ['peter', 'ryan'] }
 ]
}

I'd like to update this state to the following:

this.state = {
 teams: [ 
  {'name': 'Team1', teamMembers: ['adam'] },
  {'name': 'Team2', teamMembers: ['peter', 'ryan', 'jack'] }
 ]
}

How can I accomplish this?