/favicon.ico:1 Failed to load resource: the server responded with a status of 404 (Not Found)
typeof 5
'number'
type true
VM188:1 Uncaught SyntaxError: Unexpected token 'true'
typeof true
'boolean'
typeof false
'boolean'
 4 > 5
false
4 < 5
true
4 <= 5
true
2 + 2 === 4
true
# this is isequalto ===
VM462:1 Uncaught SyntaxError: Invalid or unexpected token
// this is isequalto ===
undefined
5 + 1 !== 3
true
typeof "5"
'string'
5 == "5"
true
5 == Number("5")
true
Number("45")
45
not true
VM1197:1 Uncaught SyntaxError: Unexpected token 'true'
!true
false
!(4 > 5)
true
!!true
true
!!false
false
true || true
true
true || false
true
true || false
true
false || false
false
// P || Q is true if at least one of P or Q is true
undefined
// || is OR
undefined
true && true
true
true && false
false
false && true
false
false && false
false
// P && Q is true when BOTH P and Q are true.
undefined
let x = 7
undefined
x <= 8 && x > 5
true
x >= 0 and x <= 10
VM2227:1 Uncaught SyntaxError: Unexpected identifier
x >= 0 && x <= 10
true
x = 15
15
x >= 0 && x <= 10
false
//precedence  not then and then or
undefined
let s = "this is a single-quoted string"
undefined
let t = 'this is a double-quoted string"
VM2664:1 Uncaught SyntaxError: Invalid or unexpected token
let t = 'this is a double-quoted string'
undefined
s
'this is a single-quoted string'
t
'this is a double-quoted string'
s + t
'this is a single-quoted stringthis is a double-quoted string'
// + concatenates strings (glues 'em)
undefined
6 + "cows"
'6cows'
//Javascript is a stringophile language.
undefined
string(6)
VM3110:1 Uncaught ReferenceError: string is not defined
    at <anonymous>:1:1
(anonymous) @ VM3110:1
"" + 6
'6'
String(6)
'6'
String(true)
'true'
// this is casting
undefined
// a cast is a temporary request to regard an object of one type as being of another
undefined
Number("45")
45
Number("quack")
NaN
s = "abcdefghijlmnopqrstuvwxyz"
'abcdefghijlmnopqrstuvwxyz'
s.toUpperCase()
'ABCDEFGHIJLMNOPQRSTUVWXYZ'
s
'abcdefghijlmnopqrstuvwxyz'
let u = s.toUpperCase()
undefined
u
'ABCDEFGHIJLMNOPQRSTUVWXYZ'
u.toLowerCase()
'abcdefghijlmnopqrstuvwxyz'
u.length
25
u[0]
'A'
u
'ABCDEFGHIJLMNOPQRSTUVWXYZ'
u[15]
'Q'
u[25]
undefined
u.substring(2,5)
'CDE'
u.substring(2,5) + u.substring(5,7)
'CDEFG'
s
'abcdefghijlmnopqrstuvwxyz'
s.substring(2,5)
'cde'
//methods depend on the state of their object
undefined
//state: what an object KNOWS
undefined
//behavior: what an object DOES
undefined
//identity: presence in memory
undefined
s.length
25
filename = "cows.jpg"
'cows.jpg'
filename.endsWith(".jpg")
true
filename.startsWith("c")
true
filename.charAt(3)
's'
filename.includes(".jpeg")
false
filename.includes(".jpg")
true
filename.indexO("z")
VM5876:1 Uncaught TypeError: filename.indexO is not a function
    at <anonymous>:1:10
(anonymous) @ VM5876:1
filename.indexOf("z")
-1
filename
'cows.jpg'
filename.indexOf("p")
6
filename.indexOf("q")
-1