when.js

function when(constraints) {
  for(obj of constraints) {
    var ths = obj['this'];
    var d = obj['do'];
    if (ths && typeof ths === "function" && d && typeof d === "function") {
      var response = ths();
      if (response === true) return d()
    }
  }
}

when([
  {this: function() {return true}, do: function() {console.log("woo")}},
  {this: function() {return false}, do: function() {console.log("oh no")}}
])

let resp = when([
  {this: () => true, do: () => 1234}
])

console.log(resp);