medium

SomeComponent.jsx

const SomeComponent = React.createClass({
  render() {
    const items = [1, 2, 3, 4, 5, 6, 7, 8, 9].map((num, i) => {
      const className = "someComponent__list__item" + i % 2 === 1 ?
                        "someComponent__list__item--odd" : "";
      
      return (
        <li className={className}>
          {num}
        </li>
      );
    });
    
    return (
      <div className="someComponent">
        <ul className="someComponent__list">
          {items}
        </ul>
      </div>
    );
  }
});

someComponent.less

.someComponent
  &__list
    padding 0
    list-style none
    &__item
      line-height 1.5
      &--odd
        background-color #efefef