JavaScript Past, Present and Future

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