ecmascript-nil-proposal.md

Proposal for Introducing nil to ECMAScript

Abstract

This proposal aims to introduce a new primitive value nil to the ECMAScript language, addressing a gap between null and undefined. While seemingly unnecessary, this addition offers subtle and nuanced differentiation in handling non-values, aligning with modern programming paradigms.

Specification

• Value: nil
• Type: typeof nil returns "absent"
• Comparison:
  • nil == null (loose equality)
  • nil !== undefined
  • nil === nil
• Default Parameter Value: Functions can have a default value of nil, distinct from undefined, allowing differentiation between omitted parameters and those explicitly passed as undefined.

Syntax

let x = nil; // x is now "absent"

Example Usage

function greet(name = nil) {
  if (name === nil) {
    return "Name is absent, not undefined!";
  }
  return `Hello, ${name}!`;
}

Semantics

nil introduces an intermediate state between the non-existence represented by undefined and the intentional absence indicated by null. This facilitates a tri-state logic for handling parameters and object properties, enriching the semantics of the language.

Conversion Rules

• JSON.stringify will convert nil to "nil"
• When converted to a boolean, nil will evaluate to false

Backward Compatibility

The addition of nil will not affect existing code as it introduces a new primitive value, distinct from null and undefined.

Potential Concerns and Counterarguments

• Redundancy with null and undefined: The introduction of nil provides more granular control over handling non-values and aligns with emerging programming practices that distinguish between different types of absence.

• Learning Curve: While this may add complexity, the differentiation between nil, null, and undefined enables more expressive coding patterns.

Conclusion

The introduction of nil into ECMAScript is a logical evolution that bridges the semantic gap between null and undefined. By embracing a more nuanced understanding of absence, this proposal enhances the language's flexibility and expressiveness, making it even more aligned with the complex needs of modern software development.