Objectives

Asynchronous JS

Identify JavaScript as a language that utilizes an event loop model

• JS uses an event loop model of execution.
  • Components include the call stack and a message queue.

Identify JavaScript as a single threaded language

• Single-threaded execution : Only one command can be processed at a time.
  • Javascript is a single-threaded language, meaning at any instance during a program only one command is being executed.

Describe the difference between asynchronous and synchronous code

• Synchronous : Means there is an inherent order among the commands and this order of execution is guaranteed. Basically will evaluate top, down - left, right.

• Asynchronous : No guarantee in the total order that commands are executed.

Execute the asynchronous function setTimeout with a callback.

function foo(food1, food2) {
  console.log(food1 + " for breakfast");
  console.log(food2 + " for lunch");
}

setTimeout(foo, 2000, "pancakes", "couscous");

Given the function predict the output of “asyncy(callback);”

"function asyncy(cb) { setTimeout(cb, 1000); console.log("async") }"

"function callback() { console.log("callback"); }",

Use setInterval to have a function execute 10 times with a 1 second period. After the 10th cycle, clear the interval.

setInterval(function () {
  console.log("hello");
}, 5000);

Write a program that accepts user input using Node’s readline module

const askGuess = () => {
  rl.question(
    "Berber asks: Can you guess how many snacks I want to eat right now? ",
    (answer) => {
      !checkGuess(Number(answer)) ? askGuess() : rl.close();
    }
  );
};