Operators priority
Operator precedence determines the order in which operators in an expression are executed. There are a number of operators that have the same precedence. In this case, the order in which operators are executed is determined by the direction of computation, which is called associativity. The direction of evaluation for operators with equal precedence can be:
 from left to right;
 from right to left.
Below is a table of all JavaScript language operators in descending order of precedence.
Priority  Operator  Associativity  Description 
0 
( ) 
– 
Grouping 
1

[ ] . new 
From left to right From left to right – 
Access to the array item.
Access to the property. Creating an object with a list of arguments 
2

function
new 
From left to right From left to right 
Function call
Creating an object without a list of arguments 
3  ++
— 
– – 
Postfix increment
Postfix decrement 
4

!
~ – ++ –– typeof void delete 
From right to left From right to left From right to left From right to left From right to left From right to left From right to left From right to left 
Logical negation
Bitwise logical negation Negation (negative number) Prefix increment Prefix decrement Type information Evaluate the expression and return undefined Deleting 
5  *
/ % 
From left to right From left to right From left to right 
Multiplication
Division Remainder of the division 
6  +
– 
From left to right From left to right 
Addition
Substraction 
7  <<
>> >> 
From left to right From left to right From left to right 
Bitwise left shift
Bitwise right shift. Bitwise unsigned right shift. 
8  <
<= > >= in instanceof 
From left to right From left to right From left to right From left to right From left to right From left to right 
Less
Less or equal More More or equal Checking if a property exists Type checking 
9  ==
!= === !== 
From left to right From left to right From left to right From left to right 
Проверка на равенство
Checking for inequality Strict equality check Checking strict inequality 
10  &  From left to right  Bitwise AND 
11  ^  From left to right  Bitwise exclusive OR (XOR) 
12    From left to right  Bitwise OR 
13  &&  From left to right  Logical AND 
14    From left to right  Logical OR 
15  ?:  From right to left  Ternary conditional operator 
16  =
+= = *= /= %= <<= >>= >>> &= ^= != 
From right to left  Varieties of the assignment operator 
17  yield  From right to left  Stopping and restoring a generator function 
18  ,  From left to right  Evaluates both operands and returns the value of the other 
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