Regular expression for this?

Question

How can I make a RegEx that matches something like these?

"Hi hello world" and "Hi world"

I tried

/^Hi (hello)? world$/i

But it doesn't work.

Answer 1

/^Hi( hello)? world$/i

The space before hello (or the one after) also needs to be optional, otherwise it matches either:

• hi__world (the underscores are "spaces")
• hi hello world

Answer 2

应该这样做：

 /^Hi( | hello )world$/i

Answer 3

试试/^Hi (hello )?world$/i ，您的代码仅匹配“ Hi hello world”和“ Hi world”

Answer 4

Hi (\hello |)world

The pipe character works as "or." So, the expression inside the parens matches either " hello" or nothing. You can test your Javascript regulare expressions here: http://rejex.heroku.com/