点代表除了换行符以外的字符，\n正好是换行符

. 应该不包含 \ 的，改下你的正则试试，

console.log(/h[.\\]+(\d+)def/g.exec(s));

试试 console.log(/h.+(\d+)def/g.exec(escape(s)));

 var s = 'hi\nabc454def';
console.log(/h[\s\S]+(\d+)def/g.exec(s));//["hi↵abc454def", "4", index: 0, input: "hi↵abc454def"]  
console.log(/h[\w\W]+(\d+)def/g.exec(s));//["hi↵abc454def", "4", index: 0, input: "hi↵abc454def"]

http://stackoverflow.com/a/1981692/2586541

js正则不支持单行模式

 console.log(/h(.|\n)+(\d+)def/g.exec(s));