javascript函数表达式

let sayHi = function() {
  alert( "Hello" );
};

function ask(question, yes, no) {
  if (confirm(question)) yes()
  else no();
}
function showOk() {
  alert( "You agreed." );
}
function showCancel() {
  alert( "You canceled the execution." );
}
// usage: functions showOk, showCancel are passed as arguments to ask
ask("Do you agree?", showOk, showCancel);

function ask(question, yes, no) {
  if (confirm(question)) yes()
  else no();
}
ask(
  "Do you agree?",
  function() { alert("You agreed."); },
  function() { alert("You canceled the execution."); }
);