toSnakeCase() and toCamelCase() as String.prototype

string.normalize.js

var hasSpace = /\s/;
var hasSeparator = /[\W_]/;
var separatorSplitter = /[\W_]+(.|$)/g;
var camelSplitter = /(.)([A-Z]+)/g;
function unseparate(string) {
  return string.replace(separatorSplitter, function (m, next) {
    return next ? ' ' + next : '';
  });
}
function uncamelize(string) {
  return string.replace(camelSplitter, function (m, previous, uppers) {
    return previous + ' ' + uppers.toLowerCase().split('').join(' ');
  });
}
String.prototype.toNoCase = function () { // https://github.com/ianstormtaylor/to-no-case
  if (hasSpace.test(this)) return this.toLowerCase();
  if (hasSeparator.test(this)) return (unseparate(this) || this).toLowerCase();
  return uncamelize(this).toLowerCase();
}
String.prototype.toSpaceCase = function () { // https://github.com/ianstormtaylor/to-space-case
  return this.toNoCase().replace(/[\W_]+(.|$)/g, function (matches, match) {
    return match ? ' ' + match : '';
  });
}
String.prototype.toSnakeCase = function () { // https://github.com/ianstormtaylor/to-snake-case
  return this.toSpaceCase().replace(/\s/g, '-');
}
String.prototype.toCamelCase = function () { // https://github.com/ianstormtaylor/to-camel-case
  return this.toSpaceCase().replace(/\s(\w)/g, function (matches, letter) {
    return letter.toUpperCase();
  });
}

As angular filters: https://gist.github.com/roylory/ad50488e35c51402b88e#file-angular_string_normalization_filters-js