Polyfill for call in JavaScript

What is Function.prototype.call?

The call method allows you to invoke a function with a specified this context and pass arguments individually. Here’s a quick example:

How we can Implement custom call

Setting Default Context:

context = context || globalThis;

• If context is null or undefined, it defaults to globalThis. This ensures the function is called in the global context when no context is provided.

Creating a Unique Key:

const uniqueKey = Symbol("fn");

• A Symbol is used to create a unique property key to avoid overwriting existing properties on the context object.

Assigning the Function to the Context:

context[uniqueKey] = this;

• The function (this refers to the function being called) is temporarily added as a property of the context object.

Calling the Function:

const result = context[uniqueKey](...args);

• The function is called with the provided arguments using the spread syntax.

Cleaning Up:

delete context[uniqueKey];

• The temporary property is removed from the context object to prevent side effects.

Returning the Result:

return result;

• The result of the function call is returned.

Comments

[Karishma]

👍