规则名 | 规则类型 |
---|---|
operator-assignment |
suggestion |
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 shorthand
选项 "always"
默认值的 错误 代码示例:
/*eslint operator-assignment: ["error", "always"]*/
x = x + y;
x = y * x;
x[0] = x[0] / y;
x.y = x.y << z;
选项 "always"
默认值的 正确 代码示例:
::: correct
/*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")
选项 "never"
的 错误 代码示例:
/*eslint operator-assignment: ["error", "never"]*/
x *= y;
x ^= (y + z) / foo();
选项 "never"
的 正确 代码示例:
::: correct
/*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.