JavaScript Fast Intro

// This is a one line comment in JavaScript. This line of code will not run.
// You create comments by adding "//" before every line.
// Comments are important to document code or explain things.

/*
This
is
a multiline comment.  Instead of writing "//" before every line
*/

// try typing these directly on your console, right after ">" and press enter.

// addition

1 + 1

// Press enter. The result should be:

> 2

// Multiplication

2 * 2

> 4

// Division

10 / 5

> 2

// Modulus or % gives the remainder of a division

10 % 2

> 0

// remainder is 0

11 % 2

> 1

// remainder is 1

// Strings: A string can be any text inside double or single quotes

"Hello"

// "hello" is a string, you can also add strings together.

"Hello" + "Everyone"

> "HelloEveryone"

// "1" is also a string. The number 1 is not the same as the string "1".
// Try adding "1" + "1" together.

"1" + "1"

// this is equal to "11"

// Booleans are either true or false

1 + 1 === 2

// true

1 + 1 === 3

// false

"1" === 1

// false

1 < 2

// true

2 < 2

// false

2 <= 2

// true, <= this is less than or equal to.  The inverse is >= greater than or equal.

11 % 2 === 1

// true

10 % 2 === 0

// true

// Exercise hint 1: Maybe something like this could be useful.

// Variables
// We can save a value in a variable for later use.
// Let's create the variable foo and assign the value 99 to it.

var foo = 99;

// let's call foo in the console.

foo

// You have called your variable foo and its value is 99
// Now, you can manipulate the value in foo if you like.

foo = foo + 1;

// call foo again and see what the value is now.

if(1 + 1 === 2){
  console.log("Hello");
}

// Since 1 + 1 === 2 is true, you should see "Hello" on the console.


if(10 / 5 === 3){
  console.log("Hello");
}

// Since 10 / 5 === 3 is false, you should NOT see "Hello" on the console.

// You can also add an else statement after the if statement
// else statements only run if the if statement is false.

if(10 / 5 === 3){
  console.log("Hello");
} else {
  console.log("10 divided by 5 does not equal 3, this is why you are seeing this message in your log.")
}

console.log(1);
console.log(2);
console.log(3);
console.log(4);
console.log(5);
...
console.log(100);

/*
for loops take in 3 arguments
first: var i = 1 is the starting point of the loop
Second: i <= 100 sets the limit
Third: i = i + 1 adds 1 to i everytime the loop starts
*/

for(var i = 1; i <= 100; i = i + 1){
  console.log(i);
}

/*
We need to increment i by one to make the loop work.
If you leave i at the initial value of 1 the second argument
i <= 100 will always be true (since i is 1, 1 will always be less than equal 100).
If i <= 100 is always true, the loop would go on forever and crash your computer.
So this is why we need to have a counter that increments in the loop (i = i + 1).
Once i is equal to 101, by adding one to i a hundred times.  The second argument would be false and
loop would terminate.  This is why we need the third argument i = i + 1
You can also write i = i + 1 like this i++
*/

// We can also have if statements inside a for loop

for(var i = 1; i <= 100; i = i + 1){
  if ( i + 5 === 10){
    console.log("Is the variable i currently 5?");
    // let's check and see, remember this line is a comment
    console.log(i);
    // check your log and see what i was.
  }
}

// Run the for loop above and see what it logs in the console.
// Remember to keep the right notation.  A missing parenthesis or curly bracket "{"
// will break your code and throw an error.

// this loop ran 100 times but only ran the if block of code when i was 5 and
// it skipped the if block of code for all the other numbers.


// Through in an else statement inside the for loop too.

for(var i = 1; i <= 5; i = i + 1){
  if ( i + 5 === 10){
    console.log("Who ate my taco?");
  } else {
    console.log(i);
  }
}

// Exercise hint 2: use a for loop with if and else statements to log the exercise problem.
// running the above loop logs the following:

> 1
> 2
> 3
> 4
> "Who ate my taco?"

// this loop ran 5 times but only when i = 5 the if statement is true and
// it logged: "Who ate my taco?",  else ran for all the other numbers logging only the variable i.

if(some condition is true){
  console.log("this");
} else if (some condition is true){
  console.log("this will run only if the first if condition is false and the else if condition is true");
} else {
  console.log("this will only run if the if statement and else if statement is false")
}

var x = 1;
var y = 2;

// && is for "and" and both conditions have to be met to be evaluate to true
// || is for "or" and only one of the conditions has to be met to evaluate to true

if(x === 1 && y > 1){
  console.log("this code will run");
}

if (x === 2 || y > 1){
  console.log("So will this code run");
}