How can I replace consecutive whitespace with a single space from the whole string

问题

I have a string with 2,3 or more spaces between non-space characters

string = "a  b c   d"

What can I do to make it like that:

output_string == "a b c d"

回答1:

The simplest way would be using Regular Expressions:

iex(1)> string = "a  b c   d"
"a  b c   d"
iex(2)> String.replace(string, ~r/ +/, " ") # replace only consecutive space characters
"a b c d"
iex(3)> String.replace(string, ~r/\s+/, " ") # replace any consecutive whitespace
"a b c d"

回答2:

For what it's worth, you don't even need the regex:

iex(3)> "a b c    d" |> String.split |> Enum.join(" ")
#=>"a b c d"

Also just from my very little bit of smoke testing, it looks like this will work with any whitespace separators (i. e. it works on spaces and tabs as far as I can tell).

回答3:

Another possibility would be to String#split and Enum#join:

iex(1)> "a  b c   d" |> String.split(~r{\s+}) |> Enum.join(" ")
#⇒ "a b c d"

回答4:

Regex.replace(~r/\s+/, "a b c d", " ")

来源：https://stackoverflow.com/questions/39393177/how-can-i-replace-consecutive-whitespace-with-a-single-space-from-the-whole-stri