正则表达式仅匹配字符或空格或两个单词之间的一个点，不允许双倍空格

Question

I need help with regular expression.I need a expression in JavaScript which allows only character or space or one dot between two words, no double space allowed.

I am using this

var regexp = /^([a-zA-Z]+\s)*[a-zA-Z]+$/;

but it's not working.

Example

1.  hello space .hello - not allowed
2.  space hello space - not allowed

Answer 1

try this:

^(\s?\.?[a-zA-Z]+)+$

EDIT1

/^(\s{0,1}\.{0,1}[a-zA-Z]+)+$/.test('space ..hello space')
false
/^(\s{0,1}\.{0,1}[a-zA-Z]+)+$/.test('space .hello space')
true

v2:

/^(\s?\.?[a-zA-Z]+)+$/.test('space .hello space')
true
/^(\s?\.?[a-zA-Z]+)+$/.test('space ..hello space')
false

v3: if you need some thisn like one space or dot between

/^([\s\.]?[a-zA-Z]+)+$/.test('space hello space')
true
/^([\s\.]?[a-zA-Z]+)+$/.test('space.hello space')
true
/^([\s\.]?[a-zA-Z]+)+$/.test('space .hello space')
false

v4:

/^([ \.]?[a-zA-Z]+)+$/.test('space hello space')
true
/^([ \.]?[a-zA-Z]+)+$/.test('space.hello space')
true
/^([ \.]?[a-zA-Z]+)+$/.test('space .hello space')
false
/^([ ]?\.?[a-zA-Z]+)+$/.test('space .hello space')
true

EDIT2 Explanation:

may be problem in \\s = [\\r\\n\\t\\f ] so if only space allowed - \\s? can be replaced with [ ]?

http://regex101.com/r/wV4yY5

Answer 2

This regular expression will match multiple spaces or dots between words and spaces before the first word or after the last word. This is the opposite of what you want, but you can always invert it ( !foo.match(...) ):

/\b[\. ]{2,}\b|^ | $/

In regex101.com: http://regex101.com/r/fT0pF2

And in plainer english:

\b        => a word boundary
[\. ]     => a dot or a space
{2,}      => 2 or more of the preceding
\b        => another word boundary
|         => OR
^{space}  => space after string start
|         => OR
{space}$  =>  space before string end

This will match:

"this  that" // <= has two spaces
"this. that" // <= has dot space
" this that" // <= has space before first word
"this that " // <= has space after last word

But it will not match:

"this.that and the other thing"

Answer 3

How about that?

^\s*([a-zA-Z]+\s?\.?[a-zA-Z]+)+$

This allows:

1. Multiple leading spaces.
2. Space as a delimiter.
3. Dot in the second and any consecutive word.

Answer 4

Try this (only a single whitespace or a period is allowed between the words):

> /\w+[\s\.]\w+/.test('foo bar')
true
> /\w+[\s\.]\w+/.test('foo.bar')
true
> /\w+[\s\.]\w+/.test('foo..bar')
false
> /\w+[\s\.]\w+/.test('foo .bar')
false