Replace multiple whitespaces with single whitespace in JavaScript string

Here's a non-regex solution (just for fun):

var s = ' a   b   word word. word, wordword word   ';

// with ES5:
s = s.split(' ').filter(function(n){ return n != '' }).join(' ');
console.log(s); // "a b word word. word, wordword word"

// or ES2015:
s = s.split(' ').filter(n => n).join(' '); 
console.log(s); // "a b word word. word, wordword word"

Can even substitute filter(n => n) with .filter(String)

It splits the string by whitespaces, remove them all empty array items from the array (the ones which were more than a single space), and joins all the words again into a string, with a single whitespace in between them.

using a regular expression with the replace function does the trick:

string.replace(/\s/g, "")

Something like this:

var s = "  a  b     c  ";

console.log(
  s.replace(/\s+/g, ' ')
)

You can augment String to implement these behaviors as methods, as in:

String.prototype.killWhiteSpace = function() {
    return this.replace(/\s/g, '');
};

String.prototype.reduceWhiteSpace = function() {
    return this.replace(/\s+/g, ' ');
};

This now enables you to use the following elegant forms to produce the strings you want:

"Get rid of my whitespaces.".killWhiteSpace();
"Get rid of my extra        whitespaces".reduceWhiteSpace();