if-then-else-if-else.js

const If = expression => {
  let call = true, value;
  return {
    then: callback => Promise.resolve(value).then(callback),
    Then(callback) {
      if (call && expression) {
        call = false;
        value = callback(expression);
      }
      return this;
    },
    ElseIf(expression) {
      return call ? If(expression) : this;
    },
    Else(callback) {
      if (call) {
        call = false;
        value = callback();
      }
      return this;
    }
  };
};

// example
If(condition1)
  .Then(value => {
    console.log(value);
  })
  .ElseIf(condition2)
  .Then(value => {
    console.log(value);
  })
  .Else(() => {
    console.log('no match');
  });

I made a react hook similar to this awhile back. running across this is funny. https://github.com/bresnow/utility-react-hooks/blob/master/src/hooks/useIf.tsx