5.2.1 Use trailing commas

Example:

5.2.2 Do not use the variadic Array constructor

The constructor is error-prone if arguments are added or removed. Use a literalinstead.

Disallowed:

const a2 = new Array(x1, x2);
const a4 = new Array();

Instead, write

Explicitly allocating an array of a given length using new Array(length) isallowed when appropriate.

5.2.3 Non-numeric properties

Do not define or use non-numeric properties on an array (other thanlength). Use a Map (or Object) instead.

5.2.4 Destructuring

let [, b,, d] = someArray;

Destructuring may also be used for function parameters (note that a parametername is required but ignored). Always specify [] as the default value if adestructured array parameter is optional, and provide default values on the lefthand side:

Disallowed:

Tip: For (un)packing multiple values into a function’s parameter or return,prefer object destructuring to array destructuring when possible, as it allowsnaming the individual elements and specifying a different type for each.

5.2.5 Spread operator

Example: