JavaScript inline switch. Useful in React render methods, and still feels like a switch statement with the checked value up top. Also allows for falsy values which I also didn't see in my casual search for similar solutions.

ISwitch

function iswitch(key, map, def) {
  return map !== null && typeof map === 'object' && map.hasOwnProperty(key) ? map[key] : def; // This way falsy values can be returned. 
}

let result = iswitch('a', {
  'a': "first value",
  'b': "second value",
}, "default value");