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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