"abc def rr tt" // should return 3
"34 45n v" // should return 2

("abc def rr tt".split(" ").length - 1)

var length = "abc def rr tt".split(" ").length - 1;

String.prototype.getWhitespaceCount = function() {
    return this.split(" ").length - 1
}

var x = "abc def rr tt";
var length = x.getWhitespaceCount();

str.split(' ').length-1

"abc def rr tt".match(/s/g).length;

str.length - str.replace(/s+/g, '').length;