@putout/plugin-optional-chaining

The optional chaining operator (?.) enables you to read the value of a property located deep within a chain of connected objects without having to check that each reference in the chain is valid.

The ?. operator is like the . chaining operator, except that instead of causing an error if a reference is nullish (null or undefined), the expression short-circuits with a return value of undefined. When used with function calls, it returns undefined if the given function does not exist.

This results in shorter and simpler expressions when accessing chained properties when the possibility exists that a reference may be missing. It can also be helpful while exploring the content of an object when there's no known guarantee as to which properties are required.

(c) MDN

🐊Putout plugin related to Optional Chaining.

Install

npm i @putout/plugin-optional-chaining

Rules

• ✅ convert-logical-to-optional;
• ✅ convert-optional-to-logical;
• ✅ convert-logical-assign-to-optional;
• ✅ convert-optional-assign-to-logical;

Config

{
    "rules": {
        "optional-chaining/convert-logical-to-optional": "on",
        "optional-chaining/convert-optional-assign-to-logical": "on",
        "optional-chaining/convert-logical-assign-to-optional": "off",
        "optional-chaining/convert-optional-to-logical": "off"
    }
}

convert-logical-to-optional

The logical AND (&&) (logical conjunction) operator for a set of boolean operands will be true if and only if all the operands are true. Otherwise it will be false.

More generally, the operator returns the value of the first falsy operand encountered when evaluating from left to right, or the value of the last operand if they are all truthy.

(c) MDN

Checkout out in 🐊Putout Editor.

❌ Example of incorrect code

const result = hello && hello.world;

if (typeof a === 'function' && a(1, 2))
    alert();

✅ Example of correct code

const result = hello?.world;

if (a?.(1, 2))
    alert();

convert-logical-assign-to-optional

Proposal to add support for optional chaining on the left of assignment operators: a?.b = c.

(c) Proposal of Optional Chaining Assignment

Disabled by default. Checkout out in 🐊Putout Editor.

❌ Example of incorrect code

if (a) {
    a.b = 5;
}

if (a)
    a.b = 5;

a && (a.b = 5);

✅ Example of correct code

a?.b = 5;

convert-optional-assign-to-logical

The JavaScript exception "invalid assignment left-hand side" occurs when there was an unexpected assignment somewhere. It may be triggered when a single = sign was used instead of == or ===.

(c) MDN

Checkout in 🐊Putout Editor.

❌ Example of incorrect code

maybeAnObj?.prop = theValue;

✅ Example of correct code

maybeAnObj && (maybeAnObj.prop = theValue);

convert-optioanl-to-logical

Disabled by default. Checkout in 🐊Putout Editor.

❌ Example of incorrect code

hello?.world?.();

✅ Example of correct code

hello && hello.world && hello.world();

License

MIT