× Terms of Use Privacy Policy

Take me back!! I want my CSS!! Click me to get back :)

×

READY FOR A NEW CAREER?

But not sure where to start? Find out if a tech career is right for you.

TAKE THE 3-MINUTE QUIZ

JavaScript operators

I’ve been discovering little oddities in JS lately, and I think it’s worthwhile to know about them, so let’s take a look.

bitwise operators

Bitwise operators treat operands (the values on either side of the operator) as a sequence of 32 bits (zeros and ones). These operators manipulate the values as binary representations and then return integers.

Left Shift Operator ( << ):

x << y

Shifts the x to the left by y bits.

Did you know:

x << y

is [almost*] the same as

x * Math.pow(2, y)

Example of usage:

console.log(10 * Math.pow(2, 10)); // logs 10240
console.log(10 << 10); // logs 10240

[*truncating happens!]

Right Shift Operator ( >> ):

x >> y

Shifts the x to the right by y bits.

Example of usage: You can parse hexadecimal values to get RGB color values

var hex = 'FFEFD5'; // papayawhip
var rgb = parseInt(hex, 16); // value: 16773077

var red   = (rgb >> 16) & 0xFF; // value: 255 
var green = (rgb >> 8) & 0xFF; // value: 239
var blue  = rgb & 0xFF; // value 213

(there are other bitwise operators in the spec, I’m just highlighting those interesting me to me here).

Note: JavaScript numbers are technically stored in 64-bits, but are treated as 32 bit when bitwise operators are used.

Also Note: There are a lot of dirty things you can do with bitwise operators, and I do not suggest them. One interesting implementation could be to store boolean flag information, one integer could hold 32 flags!

converting a string to an integer with + and -

I definitely do not recommend this, but it’s worth knowing about in case of extreme debugging.

var wat = +"7", 
    meep = -"7", 
    tinyKitten = +"tiniest of kittens";

console.log(wat); // logs 7
console.log(typeof wat); // logs "number"

console.log(meep); // logs -7
console.log(typeof meep); // logs "number"

console.log(tinyKitten); // logs NaN
console.log(typeof tinyKitten) // logs "number"

difference between i++ and ++i (same for decrement)

++i returns the value of i after being incremented

i++ returns the value of i before incrementing

var i = 0, j = 0;

console.log(++i); // logs 1
console.log(i++); // logs 0

! and type casting

Did you know that the ! operator will cast the type of objects, etc. as boolean?

var kitten = {}, 
    newKitten = !kitten, 
    newerKitten = !!kitten;

console.log(typeof kitten) // logs "object"
console.log(newKitten); // logs false
console.log(typeof newKitten); // logs "boolean"
console.log(newerKitten); // logs true

Remember the !! is not a new operator, it’s just the ! (negation) operator twice. It’s still interesting/strange to me that it would cast the type.

If this kind of thing is interesting to you, I highly recommend reading through the docs or MDN’s nice bitwise summary.

Also, I’d love if you’d leave your favorite lesser known JS features in the comments!

Your email address will not be published.

0 comments

Want more articles like this?

Sign up to get the most recent tech news, tips and career advice.