javascript 如何把 正则字符串 转为为正则对象？

`
/a.*?b/
/a(.*?)c/gim
`.split(/\n/g).filter(item => !!item.trim()).map(item => {
    item = item.trim()
    let str = item.replace(/^\/(.*)\/([a-z]*)$/, '$1')
    let args = item.replace(/^\/(.*)\/([a-z]*)$/, '$2')
    return new RegExp(str, args)
})