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JavaScript - Operators Precedence



JavaScript Operators Precedence

Operator precedence (order of operations) is a collection of rules that reflect conventions about which procedures to perform first in order to evaluate a given expression.

For example, multiplication has higher precedence than addition. Thus, the expression 1 + 2 × 3 is interpreted to have the value 1 + (2 × 3) = 7, and not (1 + 2) × 3 = 9. When exponent is used in the expression, it has precedence over both addition and multiplication. Thus 3 + 52 = 28 and 3 × 52 = 75.

Operator Associativity

Operator associativity is the direction in which an expression is evaluated. For example:

var x = 10;
var y = 20;

//associativity of = operator is
//Left to Right, hence x will become 20
x = y;

As the associativity of = is left to right. Hence x is assigned the value of y.

Example:

The example below illustrates the operator precedence in JavaScript.

var txt, retval1, retval2, retval3;

//evaluates 5 * 2 first
retval1 = 15 - 5 * 2;

//above expression is equivalent to
retval2 = 15 - (5 * 2);

//forcing compiler to evaluate 15 - 5 first
retval3 = (15 - 5) * 2;

txt = "15 - 5 * 2 = " + retval1 + "<br>";
txt = txt + "15 - (5 * 2) = " + retval2 + "<br>";
txt = txt + "(15 - 5) * 2 = " + retval3 + "<br>";

The output (value of txt) after running above script will be:

15 - 5 * 2 = 5
15 - (5 * 2) = 5
(15 - 5) * 2 = 20

JavaScript Operators Precedence Table

The following table lists the precedence and associativity of JavaScript operators. Operators are listed top to bottom, in descending precedence. Operators with higher precedence are evaluated before operators with relatively lower precedence. When operators have the same precedence, associativity of the operators determines the order in which the operations are performed.

PrecedenceOperatorDescriptionAssociativity
21( )GroupingNA
20newnew (with argument list)
.Member AccessLeft to Right
[ ]Computed Member Access
( )Function Call
?.Optional chaining
19newnew (without argument list)Right to Left
18a++  a--Postfix Increment, Postfix DecrementNA
17!Logical NOTRight to Left
~Bitwise NOT
+a  -aUnary plus, Unary negation
++a  --aPrefix Increment, Prefix Decrement
typeofType
voidvoid operator
deletedelete operator
awaitawait operator
16**Exponentiation
15*  /  %Multiplication, Division, RemainderLeft to Right
14+  -Addition, Subtraction
13<<  >>  >>>Bitwise left shift, right shift and unsigned right shift
12<  <=  >  >=Less than, Less than or equal, Greater than, and Greater than or equal
inProperty in Object
instanceofInstance of Object
11==  !=Equality, Inequality
===  !==Strict Equality, Strict Inequality
10&Bitwise AND
9^Bitwise XOR
8|Bitwise OR
7&&Logical AND
6||Logical OR
5??Nullish coalescing operator
4?:Conditional (ternary) operatorRight to Left
3=Direct assignment
+=  -=  **=  *=  /=  %=Compound assignment by sum, difference, exponentiation, product, quotient and remainder
<<=  >>=  >>>=Compound assignment by Bitwise left shift, right shift and unsigned right shift
&=  ^=  |=Compound assignment by Bitwise AND, XOR and OR
&&=  ||=Compound assignment by Logical AND, OR
??=Compound assignment by nullish coalescing operator
2yield  yield*Pause Function
1,Comma / SequenceLeft to Right

❮ JavaScript - Operators

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