Disallow assignments where both sides are exactly the same


Using the recommended config from @eslint/js in a configuration file enables this rule

Self assignments have no effect, so probably those are an error due to incomplete refactoring. Those indicate that what you should do is still remaining.

foo = foo;
[bar, baz] = [bar, qiz];

Rule Details

This rule is aimed at eliminating self assignments.

Examples of incorrect code for this rule:

Open in Playground
/*eslint no-self-assign: "error"*/

foo = foo;

[a, b] = [a, b];

[a, ...b] = [x, ...b];

({a, b} = {a, x});

foo &&= foo;
foo ||= foo;
foo ??= foo;

Examples of correct code for this rule:

Open in Playground
/*eslint no-self-assign: "error"*/

foo = bar;
[a, b] = [b, a];

// This pattern is warned by the `no-use-before-define` rule.
let foo = foo;

// The default values have an effect.
[foo = 1] = [foo];

// non-self-assignments with properties.
obj.a = obj.b;
obj.a.b = obj.c.b;
obj.a.b = obj.a.c;
obj[a] = obj["a"];

// This ignores if there is a function call.
obj.a().b = obj.a().b;
a().b = a().b;

// `&=` and `|=` have an effect on non-integers.
foo &= foo;
foo |= foo;

// Known limitation: this does not support computed properties except single literal or single identifier.
obj[a + b] = obj[a + b];
obj["a" + "b"] = obj["a" + "b"];


This rule has the option to check properties as well.

    "no-self-assign": ["error", {"props": true}]
  • props - if this is true, no-self-assign rule warns self-assignments of properties. Default is true.


Examples of correct code with the { "props": false } option:

Open in Playground
/*eslint no-self-assign: ["error", {"props": false}]*/

// self-assignments with properties.
obj.a = obj.a;
obj.a.b = obj.a.b;
obj["a"] = obj["a"];
obj[a] = obj[a];

When Not To Use It

If you don’t want to notify about self assignments, then it’s safe to disable this rule.


This rule was introduced in ESLint v2.0.0-rc.0.


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