map-merge-defaults-pmb

Merge each item from an array (e.g. of options objects) with a base (e.g. an options object with default options) and optionally convert them using a custom conversion function. Supports promises and async functions.

API

This module ESM-exports one function that holds some methods:

mapMergeDefaults(base, [{how|dfKey}, ]orig[, convert])

Returns an array of the transformed items of input array orig. In the most basic mode, the transformation for each input item is just to merge it with base. You can modify the transformation by providing additional arguments:

• dfKey: If set to a non-object, acts as a shorthand for a how object with just one key dfKey, using this argument as the value.
• convert: Overrule the how option with same name (see below).
• how: An optional options object that supports these options, all optional:
  • dfKey: Default input key. If set to something other than undefined, any non-object item from orig will be objectified before merging it, by making an object with one property named the value of dfKey, and using the original item as the property value.
  • merge: A custom merge function. Can also be false, undefined or null to affirm the default, which is to use .dfMerge (default default) or .awaitMerge (default when pr option is set).
  • convert: A custom conversion function. If provided, it will receive the merge result as an additional step of the transformation. Can also be false, undefined or null to affirm the default, which is to leave the merge results as they are. If a truthy convert argument is given, it overrules this setting.
  • pr: Boolean, whether to wrap the result list in Promise.all(). Default: false. Also selects the default merge function: .dfMerge when pr is false-y, or .awaitMerge if pr is truthy. Note however that this does not add an await step before custom merge or convert functions, so in some scenarios those may need to internally await their arguments. Also base is never awaited, so you need to do that in your own code if required.

.pr(base, [{how|dfKey}, ]orig[, convert])

Like mapMergeDefaults but with the how.pr option enabled by default.

.dfMerge(base, item)

The default sync merge function. Returns { ...base, ...item }.

.awaitMerge(base, itemPr)

The default async merge function. itemPr may be a promise. Returns a promise for { ...base, ...(await itemPr) }.

Usage

see from test/usage.mjs.

Known issues

• Needs more/better tests and docs.

License

ISC