The --fix
option on the command line can automatically fix some of the problems reported by this rule.
JavaScript provides shorthand operators that combine variable assignment and some simple mathematical operations. For example, x = x + 4
can be shortened to x += 4
. The supported shorthand forms are as follows:
Shorthand | Separate -----------|------------ x += y | x = x + y x -= y | x = x - y x *= y | x = x * y x /= y | x = x / y x %= y | x = x % y x **= y | x = x ** y x <<= y | x = x << y x >>= y | x = x >> y x >>>= y | x = x >>> y x &= y | x = x & y x ^= y | x = x ^ y x |= y | x = x | y
This rule requires or disallows assignment operator shorthand where possible.
The rule applies to the operators listed in the above table. It does not report the logical assignment operators &&=
, ||=
, and ??=
because their short-circuiting behavior is different from the other assignment operators.
This rule has a single string option:
"always"
(default) requires assignment operator shorthand where possible"never"
disallows assignment operator shorthandExamples of incorrect code for this rule with the default "always"
option:
/*eslint operator-assignment: ["error", "always"]*/ x = x + y; x = y * x; x[0] = x[0] / y; x.y = x.y << z;
Examples of correct code for this rule with the default "always"
option:
/*eslint operator-assignment: ["error", "always"]*/ x = y; x += y; x = y * z; x = (x * y) * z; x[0] /= y; x[foo()] = x[foo()] % 2; x = y + x; // `+` is not always commutative (e.g. x = "abc")
Examples of incorrect code for this rule with the "never"
option:
/*eslint operator-assignment: ["error", "never"]*/ x *= y; x ^= (y + z) / foo();
Examples of correct code for this rule with the "never"
option:
/*eslint operator-assignment: ["error", "never"]*/ x = x + y; x.y = x.y / a.b;
Use of operator assignment shorthand is a stylistic choice. Leaving this rule turned off would allow developers to choose which style is more readable on a case-by-case basis.
This rule was introduced in ESLint 0.10.0.
© JS Foundation and other contributors
Licensed under the MIT License.
https://eslint.org/docs/rules/operator-assignment