var Frh = "foobar";

// ,   .

/* ,
     .
 */

/*   /*    */ SyntaxError */

var a;
console.log("The value of a is " + a); //  a undefined

console.log("The value of b is " + b); //Uncaught ReferenceError: b  

console.log("The value of c is " + c); //  c undefined
var c;

console.log("The value of x is " + x); //Uncaught ReferenceError: x  
let x;

var input;
if (input === undefined) {
  doThis();
} else {
  doThat();
}

var myArray = [];
if (!myArray[0]) {
  myFunction();
}

var a;
a + 2; // NaN

var n = null;
console.log(n * 32); //    0

if (true) {
  var x = 5;
}
console.log(x); // 5

if (true) {
  let y = 5;
}
console.log(y); // ReferenceError

/*
 * Example 1
 */
console.log(x === undefined); // true
var x = 3;

/*
 * Example 2
 */
var myvar = "my value";

(function () {
  console.log(myvar); // undefined
  var myvar = "local value";
})();

/*
 * Example 1
 */
var x;
console.log(x === undefined); // true
x = 3;

/*
 * Example 2
 */
var myvar = "my value";

(function () {
  var myvar;
  console.log(myvar); // undefined
  myvar = "local value";
})();

function do_something() {
  console.log(foo); // ReferenceError
  let foo = 2;
}

/*   */
foo(); // "bar"

function foo() {
  console.log("bar");
}

/*     */
baz(); // TypeError: baz is not a function

var baz = function () {
  console.log("bar2");
};

window.foo = "bar";

const PREFIX = "212";

//   
function f() {}
const f = 5;

//    
function f() {
  const g = 5;
  var g;

  // - 
}

const MY_OBJECT = { key: "value" };
MY_OBJECT.key = "otherValue";

var answer = 42;

answer = "Thanks for all the fish...";

x = "The answer is " + 42; // "The answer is 42"
y = 42 + " is the answer"; // "42 is the answer"

"37" - 7; // 30
"37" + 7; // "377"

"1.1" + "1.1"; // "1.11.1"
(+"1.1") + (+"1.1"); // 2.2
//    ,         .

var coffees = ["French Roast", "Colombian", "Kona"];

var fish = ["Lion", , "Angel"]; // ["Lion", undefined, "Angel"]

var myList = ["home", , "school", ]; // ["home", undefined, "school"]

var myList = [, "home", , "school"]; // [undefined, "home", undefined, "school"]

var myList = ["home", , "school", ,]; // ["home", undefined, "school", undefined]

var Sales = "Toyota";

function CarTypes(name) {
  if (name == "Honda") {
    return name;
  } else {
    return ",    " + name + ".";
  }
}

var car = { myCar: "Saturn", getCar: CarTypes("Honda"), special: Sales };

console.log(car.myCar); // Saturn
console.log(car.getCar); // Honda
console.log(car.special); // Toyota

var car = { manyCars: { a: "Saab", b: "Jeep" }, 7: "Mazda" };

console.log(car.manyCars.b); // Jeep
console.log(car[7]); // Mazda

var unusualPropertyNames = {
  "": "An empty string",
  "!": "Bang!"
}
console.log(unusualPropertyNames."");   // SyntaxError: Unexpected string
console.log(unusualPropertyNames[""]);  // "An empty string"
console.log(unusualPropertyNames.!);    // SyntaxError: Unexpected token !
console.log(unusualPropertyNames["!"]); // "Bang!"

var obj = {
  // __proto__
  __proto__: theProtoObj,
  //    handler: handler
  handler,
  // 
  toString() {
    //  
    return "d " + super.toString();
  },
  //    
  ["prop_" + (() => 42)()]: 42,
};

var foo = { a: "alpha", 2: "two" };
console.log(foo.a); // alpha
console.log(foo[2]); // two
// console.log(foo.2);            // SyntaxError: Unexpected number
// console.log(foo[a]);           // ReferenceError: a is not defined
console.log(foo["a"]); // alpha
console.log(foo["2"]); // two

var re = /ab+c/;

console.log("John's cat".length);
//    ,  .
//       10.

//      string
`In JavaScript '\n' is a line-feed.`;

//  
`In JavaScript this is
 not legal.`;

//  
var name = "",
  time = "";
` ${name},   ${time}?`;

//   HTTP ,      
POST`http://foo.org/bar?a=${a}&b=${b}
     Content-Type: application/json
     X-Credentials: ${credentials}
     { "foo": ${foo},
       "bar": ${bar}}`(myOnReadyStateChangeHandler);

"one line \n another line";

var quote = "He read \"The Cremation of Sam McGee\" by R.W. Service.";
console.log(quote); // He read "The Cremation of Sam McGee" by R.W. Service.

var home = "c:\\temp"; // c:\temp

var str =
  "this string \
is broken \
across multiple\
lines.";
console.log(str); // this string is broken across multiplelines.

var poem =
  "Roses are red,\n\
Violets are blue.\n\
I'm schizophrenic,\n\
And so am I.";