-Default value(data or function) for function parameters
-Function Declaration -> let sayHi = function() {};
-Use Arrow functions -> let sum = (a, b) => a + b;
-Pass functions by name => callOneFunction(OnotherOne);
-Object -> let obj = {};

To delete a property: delete obj.prop.

obj.property or obj[property]

let bag = {
  [fruit]: 5, // the name of the property is taken from the variable fruit
};

"key" in object

for(key in object) {
  // executes the body for each key among object properties
}

let clone = Object.assign({}, user);

let user = {
  sayHi() { // same as "sayHi: function()"
    alert("Hello");
  }
};

let user = new User();

function sumAll(...args) { // args is the name for the array
  let sum = 0;
  for (let arg of args) sum += arg;
  return sum;
}

let arr = [3, 5, 1];
alert( Math.max(...arr) ); // 5 (spread turns array into a list of arguments)