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Remainder assignment (%=)

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.

The remainder assignment (%=) operator performs remainder on the two operands and assigns the result to the left operand.

In this article

Try it

let a = 3; console.log((a %= 2)); // Expected output: 1 console.log((a %= 0)); // Expected output: NaN console.log((a %= "hello")); // Expected output: NaN

Syntax

js
x %= y

Description

x %= y is equivalent to x = x % y, except that the expression x is only evaluated once.

Examples

Using remainder assignment

js
let bar = 5; bar %= 2; // 1 bar %= "foo"; // NaN bar %= 0; // NaN let foo = 3n; foo %= 2n; // 1n

Specifications

Specification
ECMAScript® 2027 Language Specification
# sec-assignment-operators

Browser compatibility

Enable JavaScript to view this browser compatibility table.

See also

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  1. JavaScript
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  3. JavaScript Guide
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    15. JavaScript typed arrays
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    17. Resource management
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  4. Intermediate
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  5. Advanced
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  6. References
  7. Built-in objects
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  8. Expressions & operators
    1. Addition (+)
    2. Addition assignment (+=)
    3. Assignment (=)
    4. async function expression
    5. async function* expression
    6. await
    7. Bitwise AND (&)
    8. Bitwise AND assignment (&=)
    9. Bitwise NOT (~)
    10. Bitwise OR (|)
    11. Bitwise OR assignment (|=)
    12. Bitwise XOR (^)
    13. Bitwise XOR assignment (^=)
    14. class expression
    15. Comma operator (,)
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    37. Left shift assignment (<<=)
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    40. Logical AND (&&)
    41. Logical AND assignment (&&=)
    42. Logical NOT (!)
    43. Logical OR (||)
    44. Logical OR assignment (||=)
    45. Multiplication (*)
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    47. new
    48. new.target
    49. null
    50. Nullish coalescing assignment (??=)
    51. Nullish coalescing operator (??)
    52. Object initializer
    53. Operator precedence
    54. Optional chaining (?.)
    55. Property accessors
    56. Remainder (%)
    57. Remainder assignment (%=)
    58. Right shift (>>)
    59. Right shift assignment (>>=)
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    43. SyntaxError: incomplete quantifier in regular expression
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    48. SyntaxError: invalid class set operation in regular expression
    49. SyntaxError: invalid decimal escape in regular expression
    50. SyntaxError: invalid identity escape in regular expression
    51. SyntaxError: invalid named capture reference in regular expression
    52. SyntaxError: invalid property name in regular expression
    53. SyntaxError: invalid range in character class
    54. SyntaxError: invalid regexp group
    55. SyntaxError: invalid regular expression flag "x"
    56. SyntaxError: invalid unicode escape in regular expression
    57. SyntaxError: JSON.parse: bad parsing
    58. SyntaxError: label not found
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    60. SyntaxError: missing ) after argument list
    61. SyntaxError: missing ) after condition
    62. SyntaxError: missing ] after element list
    63. SyntaxError: missing } after function body
    64. SyntaxError: missing } after property list
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    66. SyntaxError: missing formal parameter
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    70. SyntaxError: new keyword cannot be used with an optional chain
    71. SyntaxError: nothing to repeat
    72. SyntaxError: numbers out of order in {} quantifier.
    73. SyntaxError: octal escape sequences can't be used in untagged template literals or in strict mode code
    74. SyntaxError: parameter after rest parameter
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    77. SyntaxError: raw bracket is not allowed in regular expression with unicode flag
    78. SyntaxError: redeclaration of formal parameter "x"
    79. SyntaxError: reference to undeclared private field or method #x
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    85. SyntaxError: tagged template cannot be used with optional chain
    86. SyntaxError: Unexpected '#' used outside of class body
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    91. SyntaxError: Using //@ to indicate sourceURL pragmas is deprecated. Use //# instead
    92. TypeError: 'caller', 'callee', and 'arguments' properties may not be accessed
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    96. TypeError: "x" is not a function
    97. TypeError: "x" is not a non-null object
    98. TypeError: "x" is read-only
    99. TypeError: already executing generator
    100. TypeError: BigInt value can't be serialized in JSON
    101. TypeError: calling a builtin X constructor without new is forbidden
    102. TypeError: can't access/set private field or method: object is not the right class
    103. TypeError: can't assign to property "x" on "y": not an object
    104. TypeError: can't convert BigInt to number
    105. TypeError: can't convert x to BigInt
    106. TypeError: can't define property "x": "obj" is not extensible
    107. TypeError: can't delete non-configurable array element
    108. TypeError: can't redefine non-configurable property "x"
    109. TypeError: can't set prototype of this object
    110. TypeError: can't set prototype: it would cause a prototype chain cycle
    111. TypeError: cannot use 'in' operator to search for 'x' in 'y'
    112. TypeError: class constructors must be invoked with 'new'
    113. TypeError: cyclic object value
    114. TypeError: derived class constructor returned invalid value x
    115. TypeError: getting private setter-only property
    116. TypeError: Initializing an object twice is an error with private fields/methods
    117. TypeError: invalid 'instanceof' operand 'x'
    118. TypeError: invalid Array.prototype.sort argument
    119. TypeError: invalid assignment to const "x"
    120. TypeError: Iterator/AsyncIterator constructor can't be used directly
    121. TypeError: matchAll/replaceAll must be called with a global RegExp
    122. TypeError: More arguments needed
    123. TypeError: null/undefined has no properties
    124. TypeError: property "x" is non-configurable and can't be deleted
    125. TypeError: Reduce of empty array with no initial value
    126. TypeError: setting getter-only property "x"
    127. TypeError: WeakSet key/WeakMap value 'x' must be an object or an unregistered symbol
    128. TypeError: X.prototype.y called on incompatible type
    129. URIError: malformed URI sequence
    130. Warning: -file- is being assigned a //# sourceMappingURL, but already has one
    131. Warning: unreachable code after return statement
  14. Misc
    1. JavaScript technologies overview
    2. Execution model
    3. Lexical grammar
    4. Iteration protocols
    5. Strict mode
    6. Template literals
    7. Trailing commas
    8. Deprecated features

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