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Lodash _.extendWith


The lodash _.extendWith method is a powerful utility function that enables developers to merge and extend objects and arrays using a customizer function. This method is similar to the _.assignWith method, but has additional functionality that allows for more granular control over the resulting merged object.

The _.extendWith function takes two or more input objects and a customizer function as its arguments. The customizer function is responsible for determining how the objects should be merged. It takes four arguments: the value of the current key in the object being merged, the value of the corresponding key in the source object, the key being merged, and the full source object.

The customizer function can return three different types of values: the first value is the value of the current key in the object being merged, the second value is the value of the corresponding key in the source object, and the third value is the new value that should be used for the key. This flexibility makes the _.extendWith method incredibly versatile and can be used to create complex, deeply nested objects with ease.

Some of the key features of the lodash _.extendWith method include:

  • It can be used to merge any number of objects with any number of nested levels of keys.
  • The customizer function can be used to control how individual keys are merged, or to add new keys to the resulting object.
  • If two or more objects have the same key, the value of the key in the last object specified will be used.
  • The _.extendWith method is able to handle circular reference objects safely and efficiently.
  • The method returns a new object, leaving the original objects untouched.

Overall, the lodash _.extendWith method is a powerful and flexible tool for merging and extending objects and arrays. It enables developers to create complex, deeply nested data structures easily, and offers granular control over how keys are merged or added to the resulting object.