/**
* 字符串前后去除空格
*
* @param {string} str 要修剪的字符串,可以为空
* @return {string} 除去空格后的字符串,可能为null
* @example
* trim(null) = null
* trim('') = ''
* trim(' ') = ''
* trim('abc') = 'abc'
* trim(' abc ') = 'abc'
*/
declare function trim(str: string): string;
export default trim;