objectAssignSpreads

Prefer object spread syntax over Object.assign() when the first argument is an object literal.

✅ This rule is included in the ts stylistic and stylisticStrict presets.

Object spread syntax ({ ...source }) provides a more concise and readable way to copy and merge objects compared to Object.assign(). When Object.assign() is called with an object literal as its first argument, the same result can be achieved more idiomatically using spread syntax.

This rule flags cases where Object.assign({}, source) or Object.assign({ prop: value }, source) can be replaced with { ...source } or { prop: value, ...source }.

const 
const clone: Record<string, unknown>
clone = 
var Object: ObjectConstructor
Provides functionality common to all JavaScript objects.
Object.
ObjectConstructor.assign<{}, Record<string, unknown>>(target: {}, source: Record<string, unknown>): Record<string, unknown> (+3 overloads)
Copy the values of all of the enumerable own properties from one or more source objects to a
target object. Returns the target object.
@param ― target The target object to copy to.
@param ― source The source object from which to copy properties.
assign({}, 
const source: Record<string, unknown>
source);

const 
const merged: Record<string, unknown>
merged = 
var Object: ObjectConstructor
Provides functionality common to all JavaScript objects.
Object.
ObjectConstructor.assign<{}, Record<string, unknown>, Record<string, unknown>>(target: {}, source1: Record<string, unknown>, source2: Record<string, unknown>): Record<string, unknown> (+3 overloads)
Copy the values of all of the enumerable own properties from one or more source objects to a
target object. Returns the target object.
@param ― target The target object to copy to.
@param ― source1 The first source object from which to copy properties.
@param ― source2 The second source object from which to copy properties.
assign({}, 
const defaults: Record<string, unknown>
defaults, 
const userConfig: Record<string, unknown>
userConfig);

const 
const extended: {
    id: number;
} & Record<string, unknown>
extended = 
var Object: ObjectConstructor
Provides functionality common to all JavaScript objects.
Object.
ObjectConstructor.assign<{
    id: number;
}, Record<string, unknown>>(target: {
    id: number;
}, source: Record<string, unknown>): {
    id: number;
} & Record<string, unknown> (+3 overloads)
Copy the values of all of the enumerable own properties from one or more source objects to a
target object. Returns the target object.
@param ― target The target object to copy to.
@param ― source The source object from which to copy properties.
assign({ 
id: number
id: 1 }, 
const data: Record<string, unknown>
data);

const 
const result: any
result = 
var Object: ObjectConstructor
Provides functionality common to all JavaScript objects.
Object.
ObjectConstructor.assign(target: object, ...sources: any[]): any (+3 overloads)
Copy the values of all of the enumerable own properties from one or more source objects to a
target object. Returns the target object.
@param ― target The target object to copy to.
@param ― sources One or more source objects from which to copy properties
assign({ 
name: string
name: "test" });

const 
const clone: {
    [x: string]: unknown;
}
clone = { ...
const source: Record<string, unknown>
source };

const 
const merged: {
    [x: string]: unknown;
}
merged = { ...
const defaults: Record<string, unknown>
defaults, ...
const userConfig: Record<string, unknown>
userConfig };

const 
const extended: {
    id: number;
}
extended = { 
id: number
id: 1, ...
const data: Record<string, unknown>
data };

const 
const result: {
    name: string;
}
result = { 
name: string
name: "test" };


var Object: ObjectConstructor
Provides functionality common to all JavaScript objects.
Object.
ObjectConstructor.assign<Record<string, unknown>, Record<string, unknown>>(target: Record<string, unknown>, source: Record<string, unknown>): Record<string, unknown> (+3 overloads)
Copy the values of all of the enumerable own properties from one or more source objects to a
target object. Returns the target object.
@param ― target The target object to copy to.
@param ― source The source object from which to copy properties.
assign(
const existingObject: Record<string, unknown>
existingObject, 
const newProperties: Record<string, unknown>
newProperties);

Options

This rule is not configurable.

When Not To Use It

If your codebase needs to support older JavaScript environments (pre-ES2018) that don’t have native spread syntax support, you may need to disable this rule or use a transpiler. Alternately, some projects may prefer to use Object.assign() for its mutability, or may use it in many places where spread syntax is not appropriate and prefer always using it for consistency.

Equivalents in Other Linters

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objectAssignSpreads

Examples

Options

When Not To Use It

Further Reading

Equivalents in Other Linters