> x = "abcdefg"
"abcdefg"
> x[0]
"a"
> x.charAt(0)
"a"
> x[0] = "A"
"A"
> x
"abcdefg"
> x[0].toUpperCase() + x.substring(1)
"Abcdefg"
> x
"abcdefg"
> x.substring(1,3)
"bc"
> x.substr(1, 2)
"bc"
> x.startsWith("abc")
true
> x.startsWith("bcd")
false
> x.endsWith("defg")
true
> x.includes("def")
true
> x
"abcdefg"
> x.indexOf("bc")
1
> x
"abcdefg"
> x.indexOf("f")
5
> let pal = "amanaplanacanalpanama"
undefined
> pal.indexOf("p")
5
> pal.lastIndexOf("p")
15
> pal.indexOf("p", 7)
15
> "meow ".repeat(10)
"meow meow meow meow meow meow meow meow meow meow "
> "*"*40
NaN
> "*".repeat(40)
"****************************************"
> "I hate spaces   so I am going to get rid of 'em. '".replace(" ", "")
"Ihate spaces   so I am going to get rid of 'em. '"
> "I hate spaces   so I am going to get rid of 'em. '".replaceAll(" ", "")
"IhatespacessoIamgoingtogetridof'em.'"
> "   48  ".trim()
"48"
> Number("   48  ".trim())
48
> typeof Number("   48  ".trim())
"number"
> x = [
  
]
Array []

> x.push("cows")
1
> x
Array [ "cows" ]

> x[0]
"cows"
> x.push(42)
2
> x
Array [ "cows", 42 ]

> x.push(True)
Uncaught ReferenceError: True is not defined
    <anonymous> debugger eval code:1
debugger eval code:1:1
> x.push(true)
3
> x
Array(3) [ "cows", 42, true ]

> y = x.push("cat")
4
> y
4
> x
Array(4) [ "cows", 42, true, "cat" ]
    0: "cows"
    1: 42
    2: true
    3: "cat"
    length: 4
    <prototype>: Array []

> x[0]
"cows"
> x[1]
42
> x[2]
true
> //Indexing works the same for strings and arrays
undefined
> [1,2,3] + [4,5,6]
"1,2,34,5,6"
> [1,2,3].concat([4,5,6])
Array(6) [ 1, 2, 3, 4, 5, 6 ]

> String([1,2,3])
"1,2,3"
> //Difference:  concat glues arrays, + is worthless
undefined
> let x = [1,2,3,4]
undefined
> x.includes(4)
true
> x.includes([3,4])
false
> let sigorney = [1,2,3, [4,5,6]]
undefined
> //puzzler: how do I get 4 to print out?
undefined
> sigorney.length
4
> sigorney[3]
Array(3) [ 4, 5, 6 ]

> signorney[3][1]
Uncaught ReferenceError: signorney is not defined
    <anonymous> debugger eval code:1
debugger eval code:1:1
> sigorney[3][1]
5
> sigorney[3][0]
4
> let y = ["cat", "elephant", "rhino"]
undefined
> y[1]
"elephant"
> y[1][3]
"p"
> y
Array(3) [ "cat", "elephant", "rhino" ]

> let z = y.pop()
undefined
> z
"rhino"
> y
> Array [ "cat", "elephant" ]

> let w = y.pop(0)
undefined
> w
"elephant"
> y
Array [ "cat" ]

> y.unshift("dog")
2
> y
Array [ "dog", "cat" ]

> z = [0,0,0,0,0,0,0,0,0,0]
Array(10) [ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 ]

> z.fill(1)
Array(10) [ 1, 1, 1, 1, 1, 1, 1, 1, 1, 1 ]

> z
Array(10) [ 1, 1, 1, 1, 1, 1, 1, 1, 1, 1 ]

> z.fill(2, 4)
Array(10) [ 1, 1, 1, 1, 2, 2, 2, 2, 2, 2 ]

> z.fill(3,2, 7)
Array(10) [ 1, 1, 3, 3, 3, 3, 3, 2, 2, 2 ]

> for(k of z){console.log(k);}
1 
1 
3 
3 
3 
3 
3 
2 
2 
2 
undefined