es-toolkit/docs/reference/compat/function/bindKey.md

bindKey

::: 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. :::

Creates a function that invokes the method at object[key] with partialArgs prepended to the arguments it receives.

This method differs from bind by allowing bound functions to reference methods that may be redefined or don't yet exist.

The bindKey.placeholder value, which defaults to a symbol, may be used as a placeholder for partially applied arguments.

Signature

function bindKey<T extends Record<PropertyKey, any>, K extends keyof T>(
  object: T,
  key: K,
  ...partialArgs: any[]
): T[K] extends (...args: any[]) => any ? (...args: any[]) => ReturnType<T[K]> : never;

namespace bindKey {
  placeholder: symbol;
}

Parameters

• object (T): The object to bind and call the method on.
• key (K): The key of the method to bind.
• partialArgs (any[]): The arguments to be partially applied.

Returns

(T[K] extends (...args: any[]) => any ? (...args: any[]) => ReturnType<T[K]> : never): Returns the new bound function.

Example

import { bindKey } from 'es-toolkit/compat';

const object = {
  user: 'fred',
  greet: function (greeting, punctuation) {
    return greeting + ' ' + this.user + punctuation;
  },
};

let bound = bindKey(object, 'greet', 'hi');
bound('!');
// => 'hi fred!'

object.greet = function (greeting, punctuation) {
  return greeting + 'ya ' + this.user + punctuation;
};

bound('!');
// => 'hiya fred!'

// Bound with placeholders.
bound = bindKey(object, 'greet', bindKey.placeholder, '!');
bound('hi');
// => 'hiya fred!'