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Map object keys and values into a new object

License: MIT License

JavaScript 79.68% TypeScript 20.32%

map-obj's Introduction

map-obj

Map object keys and values into a new object

Install

npm install map-obj

Usage

import mapObject, {mapObjectSkip} from 'map-obj';

const newObject = mapObject({foo: 'bar'}, (key, value) => [value, key]);
//=> {bar: 'foo'}

const newObject = mapObject({FOO: true, bAr: {bAz: true}}, (key, value) => [key.toLowerCase(), value]);
//=> {foo: true, bar: {bAz: true}}

const newObject = mapObject({FOO: true, bAr: {bAz: true}}, (key, value) => [key.toLowerCase(), value], {deep: true});
//=> {foo: true, bar: {baz: true}}

const newObject = mapObject({one: 1, two: 2}, (key, value) => value === 1 ? [key, value] : mapObjectSkip);
//=> {one: 1}

API

mapObject(source, mapper, options?)

source

Type: object

The source object to copy properties from.

mapper

Type: (sourceKey, sourceValue, source) => [targetKey, targetValue, mapperOptions?] | mapObjectSkip

A mapping function.

mapperOptions

Type: object

shouldRecurse

Type: boolean
Default: true

Whether targetValue should be recursed.

Requires deep: true.

options

Type: object

deep

Type: boolean
Default: false

Recurse nested objects and objects in arrays.

target

Type: object
Default: {}

The target object to map properties on to.

mapObjectSkip

Return this value from a mapper function to exclude the key from the new object.

import mapObject, {mapObjectSkip} from 'map-obj';

const object = {one: 1, two: 2}
const mapper = (key, value) => value === 1 ? [key, value] : mapObjectSkip
const result = mapObject(object, mapper);

console.log(result);
//=> {one: 1}

filter-obj - Filter object keys and values into a new object

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map-obj's Issues

Pass arguments to mapArray

Hey,

I just looked through your code to see if your package does what I need.
This library could consume less memory (I think) by moving mapArray out of mapObj and pass the arguments along - just like you pass them into mapObj.
Currently a new function is created for each recursive call. For big objects that might be quite some memory, I guess.

SyntaxError: missing = in const declaration (Firefox)

Index.js line 28 , const used in iterator for loop , should be let or var. It breaks in old browser (Firefox 46.0.1) with following error https://developer.mozilla.org/pt-BR/docs/Web/JavaScript/Reference/Errors/Missing_initializer_in_const

Add a third parameter to the result that indicates whether to go deeper

mapObject(schema, (key, value) => {
  let goDeeper = true;

  if (key === 'MAGIC_VALUE') {
    goDeeper = false;
  }

  return [
    key,
    value,
    goDeeper,
  ];
}, {
  deep: true,
});

This would be useful when the intent is to modify only a subset of the schema.

Add ability to remove a key

Would you accept a pull request which implements the following?

mapObject({one: 1, two: 2}, (key, value) => value === 1 ? [key, value] : null);
//=> {one: 1}

The code change will look like this

-let [newKey, newValue, {shouldRecurse = true} = {}] = mapper(key, value, object);
+let mapResult = mapper(key, value, object)
+if (mapResult === null) continue
+let [newKey, newValue, {shouldRecurse = true} = {}] = mapResult

Publish new release

Hi, is it possible for you to publish a new release ?
I would like to have the new shouldRecurse feature.
Thanks.

TypeError: Invalid value used as weak map key

Sorry, I opened an issue in your oher repo, not sure where I should open this issue

TypeError: Invalid value used as weak map key
    at WeakMap.set (native)
    at mapObj (/home/jperelli/celerative/wysh/WYSHAPI/node_modules/map-obj/index.js:23:7)
    at module.exports (/home/jperelli/celerative/wysh/WYSHAPI/node_modules/camelcase-keys/index.js:16:9)

What could be causing this error?

Problem with recurse nested objects

I found that if you have a Blob instance or File instance within object which passed in mapObject and deep is true the function will go inside this objects. I guess it is not correct because Blob and File are js's special objects and this logic breaks them. If you add a simple check like !(value instanceof Blob) here that will fix this problem. I can create PR.

very good

Access to parent key

Hey,

I have a use case where I don't map keys but values.
It would be useful for me to be able to access the parent's key (which is unchanged in my case) or even a list of all parents, grand-parents etc.

I realize that when mapping keys this may not make much sense but I also think there could be use cases.

Provide dot-prop-like keys

Useful for pinpointing exactly where a key is in an object. Useful to determine where a key is located in a deep object:

const mapObject = require("map-obj")

mapObject({
	a: {
		b: "🦄"
	}
}, (key, value) => {
	console.log(key)

	return [key, value]
}, {
	deep: true,
	dotPropKeys: true
})
//=> "a"
//=> "a.b"

`proto` keys assign to the prototype

If a mapper function produces ['__proto__', value], rather than create a corresponding own property, mapObject sets the prototype of the target object to the output value.

This prevents objects containing __proto__ keys from round-tripping through the identity function, and prevents mappers from producing __proto__ keys.

One possible fix is to use Object.defineProperty() for creating properties, rather than assignment. However, this would also change mapObject's behavior in certain edge cases when given custom target objects: their setters would not invoked, their non-writable own properties would be overwritten with writable properties, and writable non-configurable own properties would throw TypeErrors. Would that be considered a breaking change?

I'll submit a PR adding failing test cases.

Throw error on Arrays.

The library is not supposed to accept arrays. And it does not throw any errors on passing one too.

const newObj = mapObject([2, 1], (key, value) => [value, key]);

console.log(newObj)
//=> outputs
[ 2, 1 ]

This is due to this check. Since arrays are objects too, It lets them slide in.

map-obj/index.js

Line 3 in 1e5c466

const isObject = value => typeof value === 'object' && value !== null;

We can use the is-plain-obj package here to check only plain objects and update the docs to clearly specify that this lib is only for plain objects.

Add async support?

import mapObject from 'map-obj-async';

const newObject = await mapObject({
   url: 'https://www.google.com/'
}, async (key, value) => [key, await fetchHtml(value)]);
//=> { url: `<!DOCTYPE html>...` }

I forked and published https://github.com/richardscarrott/map-obj-async but thought it was worth opening an issue here just in case you wanted to support it? (Although not 100% sure there's a particularly nice way to support both sync and async in a single impl.)

TypeScript 3.5 incompatible

node_modules/map-obj/index.d.ts:72:3 - error TS2344: Type 'SourceObjectType' does not satisfy the constraint '{ [key: string]: unknown; }'.
Type 'object' is not assignable to type '{ [key: string]: unknown; }'.

72 SourceObjectType,
~~~~~~~~~~~~~~~~

node_modules/p-queue/index.d.ts:79:47 - error TS2344: Type 'DefaultAddOptions' does not satisfy the constraint 'QueueAddOptions'.
Index signature is missing in type 'DefaultAddOptions'.

79 EnqueueOptionsType extends QueueAddOptions = DefaultAddOptions

allow falsy return value as a sort of "filter"

If they return a falsie value, skip this key/value pair.

It might be safest if you make them explicitly return a specific value(false or null), to guard against accidental returns of undefined.

No documentation that there is no es5 build

I have to transpile this package to make it useable for IE11. Maybe you could provide two build targets?

Or at least state clearly in the README that it is not es5.

[BUG] Incorrect `source` argument passed to the `mapper` function

Right now, the source argument passed to the mapper function is not the actual original source argument the user passed to mapObject, but the "owner" object of the key/value pair for the current iteration.

Example:

const { default: mapObject } = await import('./index.js');
const subject = { nestedA: { one: 1, two: 2 }, nestedB: { three: 3, four: 4 } };
const mapper = (key, value, source) => source !== subject ? [key + '_different', value] : [key + '_same', value];
console.log(mapObject(subject, mapper, { deep: true }));

{
  nestedA_same: { one_different: 1, two_different: 2 },
  nestedB_same: { three_different: 3, four_different: 4 }
}

Notice source is only equal to subject for the top level keys.

Fixing this would be a breaking change, so should probably be released as v6.0.0?

browserify

I know you don't want to publish babelified versions of your module, and you prefer your users takes care of that.

But in order to do that, I have to manually change map-obj package.json every time I deploy, to add:

"browserify": {
    "transform": [
      "babelify"
    ]
  }

would you accept a PR to add that code to pkg file?

Types when passing { deep: true } are wrong

The types type the key and value arguments as keys and values of the passed root object, but when passing { deep: true }, my understanding is these could be deeply nested keys and values (i.e. key: string and value: unknown)

SyntaxError: missing = in const declaration

https://github.com/sindresorhus/map-obj/blob/master/index.js#L28

this line causes an error in Firefox v49.0.1

sindresorhus / map-obj Goto Github PK

map-obj's Introduction

map-obj

Install

Usage

API

mapObject(source, mapper, options?)

source

mapper

mapperOptions

shouldRecurse

options

deep

target

mapObjectSkip

Related

map-obj's People

Contributors

Stargazers

Watchers

Forkers

map-obj's Issues

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