ant-design/components/layout/col.jsx

import React, { PropTypes } from 'react';
import classNames from 'classnames';

const stringOrNumber = PropTypes.oneOfType([PropTypes.string, PropTypes.number]);
const objectOrNumber = PropTypes.oneOfType([PropTypes.object, PropTypes.number]);

export default class Col extends React.Component {
  static propTypes = {
    span: stringOrNumber,
    order: stringOrNumber,
    offset: stringOrNumber,
    push: stringOrNumber,
    pull: stringOrNumber,
    className: PropTypes.string,
    children: PropTypes.node,
    xs: objectOrNumber,
    sm: objectOrNumber,
    md: objectOrNumber,
    lg: objectOrNumber,
  }
  render() {
    const props = this.props;
    const { span, order, offset, push, pull, className, children, ...others } = props;
    let sizeClassObj = {};
    ['xs', 'sm', 'md', 'lg'].forEach(size => {
      let sizeProps = {};
      if (typeof props[size] === 'number') {
        sizeProps.span = props[size];
      } else if (typeof props[size] === 'object') {
        sizeProps = props[size] || {};
      }
      sizeClassObj = {
        ...sizeClassObj,
        [`col-${size}-${sizeProps.span}`]: sizeProps.span !== undefined,
        [`col-${size}-order-${sizeProps.order}`]: sizeProps.order,
        [`col-${size}-offset-${sizeProps.offset}`]: sizeProps.offset,
        [`col-${size}-push-${sizeProps.push}`]: sizeProps.push,
        [`col-${size}-pull-${sizeProps.pull}`]: sizeProps.pull,
      };
    });
    const classes = classNames({
      [`col-${span}`]: span !== undefined,
      [`col-order-${order}`]: order,
      [`col-offset-${offset}`]: offset,
      [`col-push-${push}`]: push,
      [`col-pull-${pull}`]: pull,
      [className]: !!className,
      ...sizeClassObj,
    });

    return <div {...others} className={classes}>{children}</div>;
  }
}