[Solved]-What is the correct approach in React to loop through an array to build html-select list of items in a function and call it in render()?-Reactjs

Try this:

renderSelectDropdown() {
    let list = [];

    this.state.users.forEach((user, idx) =>
    {   
        let opt = this.state.info.map((item) => {
            this.state.info[user.name][item].map((s, key) => {
                <option key={key}>{s}</option>;
            })
        });

        list.push(<optgroup key={idx} label={user.title}>{opt}</optgroup>);

    });

    return list;
}

render() {
    let list = renderSelectDropdown();

    return (
        <div>
           <input type="text" name="name">
           <select>
              {list}
           </select>
        </div>
    )
 }