react how to set selected code example

Example 1: select the items from selectors in .map reactjs

{this.props.categories.map((items , index)=>{
  <option key{index}>{items.categoryName} </option>
})}

Example 2: select the items from selectors in .map reactjs

{this.props.categories.map((items , index)=>{
  <option key{index}>{items.categoryName} </option>
})}      
//// created by Aqdas