Is JavaScript's `new` Keyword More Helpful Than Harmful?

Is JavaScript's "new" Keyword Harmful?

JavaScript's "new" keyword has sparked controversy, with some arguing against its use due to perceived risks. However, a closer examination reveals numerous advantages to using "new."

Advantages of Using "new"

• Prototype inheritance: "new" enables prototype inheritance, a powerful mechanism for code reuse.
• Performance: By utilizing the prototype, "new" avoids the overhead of assigning methods to each new object, resulting in faster creation and reduced memory footprint.

Disadvantage of "new"

• Silent failure: If "new" is omitted unintentionally, the code silently fails without error.

Mitigating the Disadvantage

To address this disadvantage, a simple check can be added to each function:

function foo() {
  // If "new" is omitted, silently correct the problem
  if (!(this instanceof foo)) {
    return new foo();
  }

  // Constructor logic follows...
}

This ensures that the object is always constructed properly, eliminating the risk of silent failures.

Future-proofing

ES5 introduced strict mode, which disallows certain constructs, including "arguments.callee." Therefore, the check mentioned above may need to be modified in strict mode:

function foo() {
  // Check for "new" using new.target (ES6)
  if (!(new.target)) {
    throw new Error("Constructor called as a function");
  }

  // Constructor logic follows...
}

Conclusion

While the "new" keyword has its caveats, it remains a crucial tool in JavaScript. By understanding its advantages and mitigating its potential risks, developers can safely harness the power of "new" for object creation and code reuse.

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