no-multi-assign

Disallow use of chained assignment expressions

Chaining the assignment of variables can lead to unexpected results and be difficult to read.

(function() { const foo = bar = 0; // Did you mean `foo = bar == 0`? bar = 1; // This will not fail since `bar` is not constant. })(); console.log(bar); // This will output 1 since `bar` is not scoped. 
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Rule Details

This rule disallows using multiple assignments within a single statement.

Examples of incorrect code for this rule:

/*eslint no-multi-assign: "error"*/ let a = b = c = 5; const foo = bar = "baz"; let d = e =  c; class Foo { a = b = 10; } a = b = "quux"; 
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Examples of correct code for this rule:

/*eslint no-multi-assign: "error"*/ let a = 5; let b = 5; const c = 5; const foo = "baz"; const bar = "baz"; let d = c; let e = c; class Foo { a = 10; b = 10; } a = "quux"; b = "quux"; 
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Options

This rule has an object option:

• "ignoreNonDeclaration": When set to true, the rule allows chains that don’t include initializing a variable in a declaration or initializing a class field. Default is false.

ignoreNonDeclaration

Examples of correct code for the { "ignoreNonDeclaration": true } option:

/*eslint no-multi-assign: ["error", { "ignoreNonDeclaration": true }]*/ let a; let b; a = b = "baz"; const x = {}; const y = {}; x.one = y.one = 1; 
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Examples of incorrect code for the { "ignoreNonDeclaration": true } option:

/*eslint no-multi-assign: ["error", { "ignoreNonDeclaration": true }]*/ let a = b = "baz"; const foo = bar = 1; class Foo { a = b = 10; } 
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Related Rules

• max-statements-per-line

Version

This rule was introduced in ESLint v3.14.0.

Resources

• Rule source
• Tests source