"renderMark" is not rendering, Can anyone tell what is the issue with the below code?

[stealth-sg]

renderMark={(props) => { if (props.key === 0) { return ( <span {...props} className="example-mark"> {firstLabelText} ) } else if (props.key === noUnits) { return ( <span {...props} className="example-mark"> {lastLabelText} ) } return ( <span {...props} className="example-mark"> | ) }} .example-mark { font-family: 'Figtree-Regular'; font-size: 14px; background: #000; width: 2px; height: 15px; }

.example-mark:first-child { left: 0; }

.example-mark:last-child { right: 0; }