What does this "/^\s*$/" mean as I tried to learn it from here: but can't get it meaning?

fn: function (val) {
  return typeof val === 'string' ? 
  !/^\s*$/.test(val) : val !== undefined && val !== null;
}

What does this "/^\s*$/" mean as I tried to learn it from here: https://developer.mozilla/en/docs/Web/JavaScript/Guide/Regular_Expressions but can't get it meaning?

fn: function (val) {
  return typeof val === 'string' ? 
  !/^\s*$/.test(val) : val !== undefined && val !== null;
}

• javascript

• From the URL you wrote: ^ : Matches beginning of input. \s : Matches a single character other than white space. * : Matches the preceding expression 0 or more times. $ : Matches end of input. 1+2+3+4 : Matches a string that begin and end with 0 or many white spaces. – progysm Commented Jan 7, 2017 at 19:01
• @KavishMehta, did you accept and then unaccept my answer? Is there anything else unclear? – Max Koretskyi Commented Jan 7, 2017 at 19:35
• @Maximus sorry I double click it – Kavish Mehta Commented Jan 7, 2017 at 19:49
• @KavishMehta, no problem, just wondered if it was a glitch, good luck) – Max Koretskyi Commented Jan 7, 2017 at 20:00

3 Answers 3

This

/^\s*$/

is a RegExp object

The code snippet

/^\s*$/.test(val)

uses RegExp test method to test whether a string val is empty or only contains spaces. From the docs:

The test() method executes a search for a match between a regular expression and a specified string. Returns true or false.

If you take a look at this regex in this tutorial, it will show you the following explanation:

^ asserts position at start of the string
    \s* matches any whitespace character (equal to [\r\n\t\f\v ])
      * Quantifier — Matches between zero and unlimited times, as many times as possible, giving back as needed (greedy)
$ asserts position at the end of the string, or before the line terminator right at the end of the string (if any)

Basically, it means that:

/^...$/ 

matches a string from the beginning to the end, and

\s* 

matches zero or more occurrences of white space characters

Here ^ means the beginning of expression.

\s* means 0 or more occurrences of space characters(' ', tab etc)

$ means end of the string.

so /^\s*$/ is the regex for empty string or string with only spaces.

/^\s*$/

first /{regex is here}/ is how u write regex here

^{somethingelse}$ is meaning started and ended in the middle regex

\s is any string character

'*' means zero or more

so it means all the element is character, not a number or symbol or spaces