Javascript Regex to match only a single occurrence no more or less

Question

I have a string like below:

single-hyphen

I need to match the hyphen. However, I only want to match a single occurrence of the hyphen, no more or less.

So the string above will return true, but the two below will be false:

1. a-double-hyphen
2. nohyphen

How do I define a regex to do this?

Thanks in advance.

Answer 1

You can do this

/^[^-]+-[^-]+$/

^ depicts the start of the string

$ depicts the end of the string

[^-]+ matches 1 to many characters except -

Answer 2

/^[^-]*-[^-]*$/

字符串的开头、任意数量的非连字符、一个连字符、任意数量的非连字符、字符串的结尾。

Answer 3

奇怪（而不是 Regex ）......但为什么不呢？

2 === str.split("-").length;

Answer 4

You could use a combination of indexOf and lastIndexOf :

String.prototype.hasOne = function (character) {
    var first = this.indexOf(character);
    var last = this.lastIndexOf(character);

    return first !== -1 &&
        first === last;
};

'single-hyphen'.hasOne('-'); // true
'a-double-hyphen'.hasOne('-'); // first !== last, false
'nohyphen'.hasOne('-'); // first === -1, false

http://jsfiddle.net/cSF8T/

Answer 5

Unconventional but it works. It doesn't manipulate the string or use regex.

 // only true if only one occurrence of - exists in string
 (str.indexOf("-") + 1) % ( str.lastIndexOf("-") + 1 ) === 0

Fiddle here