Operator: typeof
show the type of the operand
Numbers
- subtract
+ add
* multiply
/ divide
% remainder
++ increment (add 1)
-- decrement (subtract 1)
** exponentiation
common increment bug(also works in decrement)
Number precision bug
number operator shortcut
price = price - 5;
price -= price; are same
Operator precedence
Precedence | Operator type | Associativity | Individual Operators |
21 | Grouping | n/a | ( … ) parenthesis |
20 | Member Access | left-to-right | … . … |
Computed Member Access | left-to-right | … [ … ] | |
new (with argument list) | n/a | new … ( … ) | |
Function Call | left-to-right | … ( … ) | |
Optional chaining | left-to-right | ?. | |
19 | new (without argument list) | right-to-left | new … |
18 | Postfix Increment | n/a | … ++ |
Postfix Decrement | … -- | ||
17 | Logical NOT | right-to-left | ! … |
Bitwise NOT | ~ … | ||
Unary Plus | + … | ||
Unary Negation | - … | ||
Prefix Increment | ++ … | ||
Prefix Decrement | -- … | ||
typeof | typeof … | ||
void | void … | ||
delete | delete … | ||
await | await … | ||
16 | Exponentiation | right-to-left | … ** … |
15 | Multiplication | left-to-right | … * … |
Division | … / … | ||
Remainder | … % … | ||
14 | Addition | left-to-right | … + … |
Subtraction | … - … | ||
13 | Bitwise Left Shift | left-to-right | … << … |
Bitwise Right Shift | … >> … | ||
Bitwise Unsigned Right Shift | … >>> … | ||
12 | Less Than | left-to-right | … < … |
Less Than Or Equal | … <= … | ||
Greater Than | … > … | ||
Greater Than Or Equal | … >= … | ||
in | … in … | ||
instanceof | … instanceof … | ||
11 | Equality | left-to-right | … == … |
Inequality | … != … | ||
Strict Equality | … === … | ||
Strict Inequality | … !== … | ||
10 | Bitwise AND | left-to-right | … & … |
9 | Bitwise XOR | left-to-right | … ^ … |
8 | Bitwise OR | left-to-right | … | … |
7 | Nullish coalescing operator | left-to-right | … ?? … |
6 | Logical AND | left-to-right | … && … |
5 | Logical OR | left-to-right | … || … |
4 | Conditional | right-to-left | … ? … : … |
3 | Assignment | right-to-left | … = … |
… += … | |||
… -= … | |||
… **= … | |||
… *= … | |||
… /= … | |||
… %= … | |||
… <<= … | |||
… >>= … | |||
… >>>= … | |||
… &= … | |||
… ^= … | |||
… |= … | |||
2 | yield | right-to-left | yield … |
yield* | yield* … | ||
1 | Comma / Sequence | left-to-right | … , … |
Strings (text)
3 styles of quotes: "", '', ``
*if you want to use special characters as Strings, use escape notation. ( \)
Using ` (backtick)
Manipulating strings
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String#Methods
using methods
Converting Between Types
using methods ( toString , Number.parseFloat("string") )
Boolean Variable
true / false
!: not
null and undefined
undefined: not initialized variable, assigned by JS
null: wipe out the variable's value, assigned by developers(manually)
*always use null!!!
Objects and Symbols
objects created by { ... }
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