no-self-assign

Disallow assignments where both sides are exactly the same

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];
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Rule Details

This rule is aimed at eliminating self assignments.

Examples of incorrect code for this rule:

/*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;
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Examples of correct code for this rule:

/*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"];
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Options

This rule has the option to check properties as well.

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

props

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

/*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];
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When Not To Use It

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

Version

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

Resources

• Rule source
• Tests source