The document contains examples demonstrating various JavaScript behaviors and edge cases involving numeric values, data types, operators, sorting arrays, optional chaining, and more. Key points covered include NaN always evaluating to false, differences between == and ===, rounding numbers, sorting arrays alphabetically instead of numerically, and optional chaining.

12. > const lol = a + b + c – f * ( n + o );
NaN

13. > NaN >= 0
false

14. > NaN <= 0
false

15. > typeof NaN
number

16. ( a + b ) + c = a + ( b + c ) // mathematically true
> 0.1 + 0.2 === 0.3
false
> ( a + b ) + c == a + ( b + c )
??

17. > 0.1 + 0.2
0.30000000000000004

18. > Math.round(0.4999999999999999722444243843710864894092082)
0
> Math.round(0.4999999999999999722444243843710864894092083)
1
I’ve got 99 problems but
JavaScript ain’t
1.0000000000000009

19. > [ 2, 10 ].sort()
[ 10, 2 ]

20. > ['10','10','10', '10', '10'].map( parseInt )
[ 10, NaN, 2, 3, 4 ]

21. > typeof undefined // undefined
> typeof true // boolean
> typeof "hello" // string
> typeof 1 // number
> typeof {lol:true} // object
> typeof [1,2,3] // object
> typeof null // object

22. > null == 0 // false
> null > 0 // false
> null < 0 // false
> null >= 0 // true
> null <= 0 // true
> Number( null ) // 0

23. > false
> null
> undefined
> ""
> 0
> NaN

24. > wat.test("javascript"); // true
> wat.test("wat r u doin"); // false
> const wat = /a/g;

25. // undefined
function troll() {
return
{
haha: "ha!"
};
}
troll();
// automatic semi-colon

26. const arr = [];
arr[1] = 1;
arr[3] = 2;
arr[10] = 3;
arr.length // 11
arr[-1] = 4;
arr.s = 5;
arr.length // 11

96. const user1 = {
firstName: "David",
lastName: "Neal",
address: {
street: "123 Main Street",
city: "Nashville",
state: "Tennessee"
}
};

97. const user1 = {
firstName: "David",
lastName: "Neal",
address: {
street: "123 Main Street",
city: "Nashville",
state: "Tennessee"
}
};
const city = user1?.address?.zipCode;

99. const v1 = falseyNullOrUndefined || "defaultValue";

100. const v1 = falseyNullOrUndefined || "defaultValue";
const v2 = onlyNullOrUndefined ?? "defaultValue";

101. globalThis = window ?? self ?? global;

102. Promise.all() –or- Promise.allSettled()

103. let config;
if (production) {
config = await import("./config.production.js");
}
reportBtn.addEventListener("click", async () => {
const reporter = await import("./reporter.js);
reporter.generateReport();
});

104. const integers = Array.from(html.matchAll(/[0-9]*/g));

105. const big = BigInt(Number.MAX_SAFE_INTEGER);
const big2 = 9007199254740991n;
const evenBigger = big + 3000000n;

109. To boldly go where NaN has
undefined before!

116. Mobile Apps
Automation / DevOps
Command Line (CLI)
Services