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Operator precedence determines the way in which operators are parsed with respect to each other. Operators with higher precedence become the operands of operators with lower precendence.

A common example:

3 + 4 * 5 // returns 23

The multiplication operator ("*") has higher precedence than the addition operator ("+"), thus the expression 4 * 5 will become the right operand of the addition instead of 3 + 4 becoming the left operand of the multiplication.

Associativity

Associativity determines the way in which operators of the same precedence are parsed. For example, consider an expression:

a OP b OP c

Left-associativity (left-to-right) means that it is processed as (a OP b) OP c, while right-associativity (right-to-left) means it is interpreted as a OP (b OP c). Assignment operators are right-associative, so you can write:

a = b = 5;

with the expected result that a and b get the value 5. This is because the assignment operator returns the value that it assigned. First, b is set to 5. Then the a is also set to 5, the return value of b = 5, aka right operand of the assignment.

Table

The following table is ordered from highest (20) to lowest (0) precedence.

Precedence Operator type Associativity Individual operators
20 Grouping n/a ( … )
19 Member Access left-to-right … . …
Computed Member Access left-to-right … [ … ]
new (with argument list) n/a new … ( … )
Function Call left-to-right … ( … )
18 new (without argument list) right-to-left new …
17 Postfix Increment n/a … ++
Postfix Decrement n/a … --
16 Logical NOT right-to-left ! …
Bitwise NOT right-to-left ~ …
Unary Plus right-to-left + …
Unary Negation right-to-left - …
Prefix Increment right-to-left ++ …
Prefix Decrement right-to-left -- …
typeof right-to-left typeof …
void right-to-left void …
delete right-to-left delete …
15 Exponentiation right-to-left … ** …
14 Multiplication left-to-right … * …
Division left-to-right … / …
Remainder left-to-right … % …
13 Addition left-to-right … + …
Subtraction left-to-right … - …
12 Bitwise Left Shift left-to-right … << …
Bitwise Right Shift left-to-right … >> …
Bitwise Unsigned Right Shift left-to-right … >>> …
11 Less Than left-to-right … < …
Less Than Or Equal left-to-right … <= …
Greater Than left-to-right … > …
Greater Than Or Equal left-to-right … >= …
in left-to-right … in …
instanceof left-to-right … instanceof …
10 Equality left-to-right … == …
Inequality left-to-right … != …
Strict Equality left-to-right … === …
Strict Inequality left-to-right … !== …
9 Bitwise AND left-to-right … & …
8 Bitwise XOR left-to-right … ^ …
7 Bitwise OR 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* right-to-left yield* …
1 Spread n/a ... …
0 Comma / Sequence left-to-right … , …