extendWith

INFO

This function is only available in es-toolkit/compat for compatibility reasons. It either has alternative native JavaScript APIs or isn’t fully optimized yet.

When imported from es-toolkit/compat, it behaves exactly like lodash and provides the same functionalities, as detailed here.

Assigns properties from multiple source objects to a target object. You can provide a getValueToAssign function to determine what value will be assigned for each property.

This function merges the properties of the source objects into the target object, including properties from the prototype chain. If a property in the source objects is equal to the corresponding property in the target object, it will not be overwritten.

Unlike assignIn, this method accepts a getValueToAssign function that determines the final value to be assigned to each property in the target object. The return value of this function will be directly assigned to the corresponding property. This allows for more precise control over how properties are merged between objects. If not provided, the default behavior is equivalent to using the identity function (returning the source value).

Signature

function extendWith<O, S>(
  object: O,
  source: S,
  getValueToAssign?: (objValue: any, srcValue: any, key: string, object: O, source: S) => any
): O & S;
function extendWith<O, S1, S2>(
  object: O,
  source1: S1,
  source2: S2,
  getValueToAssign?: (objValue: any, srcValue: any, key: string, object: O, source: S1 | S2) => any
): O & S1 & S2;
function extendWith<O, S1, S2, S3>(
  object: O,
  source1: S1,
  source2: S2,
  source3: S3,
  getValueToAssign?: (objValue: any, srcValue: any, key: string, object: O, source: S1 | S2 | S3) => any
): O & S1 & S2 & S3;
function extendWith<O, S1, S2, S3, S4>(
  object: O,
  source1: S1,
  source2: S2,
  source3: S3,
  source4: S4,
  getValueToAssign?: (objValue: any, srcValue: any, key: string, object: O, source: S1 | S2 | S3 | S4) => any
): O & S1 & S2 & S3 & S4;
function extendWith(object: any, ...sources: any[]): any;
function extendWith(object: any, ...sources: any[]): any;

Parameters

• object (any): The target object to which properties will be assigned.
• sources (...any[]): The source objects whose properties will be assigned to the target object.

Returns

(any): The updated target object with properties from the source objects assigned.

Examples

const target = { a: 1 };
const result = assignInWith(target, { b: 2 }, { c: 3 }, function (objValue, srcValue) {
  return objValue === undefined ? srcValue : objValue;
});
console.log(result); // Output: { a: 1, b: 2, c: 3 }