正则表达式在空格之前插入逗号

Question

如何在空格之前插入N个逗号到此字符串，但不能在句点或其他逗号之后插入？使用ruby或javascript。

Answer 1

一个选项：

>>> var str = "Lorem ipsum dolor sit amet consectetur adipiscing elit. Praesent mauris neque adipiscing nec malesuada id fermentum at eros. Curabitur eu neque nunc, et porta risus.";
>>> str.replace(/([^,.]) /g, '$1, ');
"Lorem, ipsum, dolor, sit, amet, consectetur, adipiscing, elit. Praesent, mauris, neque, adipiscing, nec, malesuada, id, fermentum, at, eros. Curabitur, eu, neque, nunc, et, porta, risus."

或者，你可以采用另一种方式来mimick negative lookbehind：

>>> var str = "Lorem ipsum dolor sit amet consectetur adipiscing elit. Praesent mauris neque adipiscing nec malesuada id fermentum at eros. Curabitur eu neque nunc, et porta risus.";
>>> str.replace(/([,.])? /g, function($0, $1) { return $1 ? $0 : ', '; });
"Lorem, ipsum, dolor, sit, amet, consectetur, adipiscing, elit. Praesent, mauris, neque, adipiscing, nec, malesuada, id, fermentum, at, eros. Curabitur, eu, neque, nunc, et, porta, risus."

Answer 2

@ jensgram答案的Ruby变体：

str.gsub(/([^,.]) /, $1 + ', ')