how to set a type for key in object in react code example

Example 1: map function in react

function NameList() {
	const names = ['Bruce', 'Clark', 'Diana']
    return (
    	<div>
      {names.map(name => <h2>{name}</h2>)}
      	</div>
    )
}

Example 2: react create pillbox for each chunk of array

const brandGroups = brandNames.map((e, i) => {
      return i % chunkSize === 0 ? brandNames.slice(i, i + chunkSize) : null;
    }).filter(e => { return e; });

    const renderBrandsItems = () => {
      const ThreePlusBrands = `${brandNames.slice(0, 3).join(", ")} + ${brandNames.length - 3} more`;
      if (brandGroups.length <= 3) {
        return brandGroups.map((item, i) => {
          return (
            <div key={i}>
              <SelectionLabel>
                {item}
                <ClearIcon
                  className="fa fa-times"
                  data-name={item}
                  onClick={handleBrandClick}
                />
              </SelectionLabel>
            </div>
          );
        });
      }
      return (
        <SelectionLabel>
          {ThreePlusBrands}
          <ClearIcon className="fa fa-times" onClick={onClearBrands} />
        </SelectionLabel>
      );
    };