Javascript string presentation methods with underscore.js (upper, lower, capitalize, title)

gistfile1.js

String.prototype.upper = function() {
	return _.reduce(this.split(""), function(memo, chr) { return memo + chr.toUpperCase() }, "")
}
String.prototype.lower = function() {
	return _.reduce(this.split(""), function(memo, chr) { return memo + chr.toLowerCase() }, "")
}
String.prototype.capitalize = function() {
	return this.charAt(0).toUpperCase() + this.slice(1);
}
String.prototype.title = function() {
	return _.reduce(this.lower().split(" "), function(memo, word) { return memo + " " + word.capitalize() }, "").slice(1);
}