I have a function that is using eval to convert a string with an expression to an object based on the parameter.
let indexType = ["Mac", "User", "Line", "Mask", "Ip", "Location"]
const filterIndex = (item) => {
filteredIndexSearch = []
eval(`search${item}`).forEach((e) => filteredIndexSearch.push(searchData[e.key]))
}
filterIndex(indexType[searchTotal.indexOf(Math.max(...searchTotal))])
searchData is an array that returns values based on the user input.
searchTotal is an array with the length of each search{item} array.
The filterIndex function takes the highest value from the searchData array and corresponds it to the indexType array, then use eval to convert the string to an object to pass the value to the filteredIndexSearch array.
What would be a better alternative to eval?
EDIT
To add more information on what this does:
searchData = [
[
{
key: 1,
data: "0123456789101"
},
{
key: 1,
data: "John Smith"
}
],
[
{
key: 2,
data: "0123456789102"
},
{
key: 2,
data: "Jane Smith"
},
]
]
const search = (data, key, container) => {
if (!data) data = "";
if (data.toLowerCase().includes(string)) {
container = container[container.length] = {
key: key,
data: data
}
}
}
const returnSearch = () => {
for (let i = 0; i < searchData.length; i++) {
search(searchData[i][0].data, searchData[i][0].key, searchMac)
search(searchData[i][1].data, searchData[i][1].key, searchUser)
}
}
returnSearch()
The data is incomplete, but hopefully conveys what I'm trying to do.
search will take the user input, and store the information in the corresponding array. If I input "Jo", it will return the searchUser array with only the "John Smith" value and all the other values with the same key. Inputting "102" returns the searchMac with the "0123456789102" value and all other values with the same key.
At the end of the day. I just want to convert search${parameter} to an object without using eval.
Move your global arrays into an object.
Somewhere it appears that you're defining the arrays, something like:
searchMac = [...];
searchUser = [...];
...
Instead of defining them as individual arrays, I'd define them as properties in an object:
searchIndices.Mac = [...];
searchIndices.User = [...];
...
Then, instead of using eval, your can replace your eval().forEach with searchIndices[item].forEach.
If the order of your search isn't important, your can instead loop through the keys of searchIndices:
Object.keys(searchIndices).forEach(item => {
searchIndices[item].forEach(...);
});
This ensures that if you ever add or drop an entry in searchIndices, you won't miss it or accidentally error out on an undefined search index.
Any time you have a situation with variables named x0, x1 etc, that should be a red flag to tell you you should be using an array instead. Variable names should never be semantically meaningful - that is code should never rely on the name of a variable to determine how the code behaves. Convert search0 etc into an array of search terms. Then use:
const filterIndex = (item) => search[item].map(i => searchData[i.key]);
filteredIndexSearch = filterIndex(indexType[searchTotal.indexOf(Math.max(...searchTotal))]);
(simplifying your code). Note that in your code, filteredIndexSearch is modified inside the arrow function. Better to have it return the result as above.
Related
I have an array of objects and within those objects is another object which contains a particular property which I want to get the value from and store in a separate array.
How do I access and store the value from the name property from the data structure below:
pokemon:Object
abilities:Array[2]
0:Object
ability:Object
name:"blaze"
1:Object
ability:Object
name:"solar-power"
How would I return and display the values in the name property as a nice string like
blaze, solar-power ?
I tried doing something like this but I still get an array and I don't want to do a 3rd loop since that is not performant.
let pokemonAbilities = [];
let test = pokemon.abilities.map((poke) =>
Object.fromEntries(
Object.entries(poke).map(([a, b]) => [a, Object.values(b)[0]])
)
);
test.map((t) => pokemonAbilities.push(t.ability));
Sample Data:
"pokemon": {
"abilities": [
{
"ability": {
"name": "friend-guard",
"url": "https://pokeapi.co/api/v2/ability/132/"
},
"ability": {
"name": "Solar-flare",
"url": "https://pokeapi.co/api/v2/ability/132/"
}
}
]
}
Then I am doing a join on the returned array from above to get a formatted string.
It just seems like the multiple map() loops can be optimized but I am unsure how to make it more efficient.
Thank you.
There is no need for a loop within loop. Try this:
const pokemon = {
abilities: [{
ability: {
name: 'friend-guard',
url: 'https://pokeapi.co/api/v2/ability/132/'
},
}, {
ability: {
name: 'Solar-flare',
url: 'https://pokeapi.co/api/v2/ability/132/'
}
}]
};
const pokemonAbilities = pokemon.abilities.map(item => item.ability.name).join(', ');
console.log(pokemonAbilities);
I have an API that serves JSON data. Currently if you do api/weapons for example it gives you all the weapons available, api/weapons/weaponName gives information about that specific weapon. What I want to do is be able to api/weapons?type=sword&rarity=5 for example. I managed to pull of api/weapons?type=sword and api/weapons?rarity=5 on their own but not together.
Here's what I'm currently doing:
let filtered = [];
if (query.type) {
filtered = filtered.concat((await weapons).filter(w => formatName(w.weaponType) === formatName(query.type)));
}
if (query.rarity) {
filtered = filtered.concat((await weapons).filter(w => w.rarity == query.rarity));
}
if (!filtered.length) filtered = [await weapons]
res.status(HttpStatusCodes.ACCEPTED).send(filtered);
formatName is just a function that makes the string all lowercase and trims it and removes all spaces.
If we take api/weapons?type=sword&rarity=5
I think what's happening right now is:
It is getting all the weapons with the type "sword"
It is getting all the weapons with the rarity "5"
It is joining all the results together, so all the weapons with the type sword (regardless of rarity) and al the weapons with the rarity 5 (regardless of type).
I want it to filter weapons with ONLY that rarity AND ONLY that type. So only 5 rarity swords for example. What is the most beneficial way of handling this
I'd suggest retrieving "weapons" once and then running any filters on them without concatenating the results:
let filtered = [ ...(await weapons) ];
if (query.type) {
filtered = filtered.filter(w => w => formatName(w.weaponType) === formatName(query.type));
}
if (query.rarity) {
filtered = filtered.filter(w => w.rarity == query.rarity);
}
res.status(HttpStatusCodes.ACCEPTED).send(filtered);
Your current logic is testing whether one constraint OR another matches, what you actually need to do is to do an AND, which means you must perform the test in a single pass of filter.
I would slightly modify your code so that you compare all constraints that you're sending...you could further modify the logic below to accept a logical operator to test whether the rarity is >= or <= to a certain number for example.
const weapons = [{
type: 'sword',
name: 'swift blade of zek',
rarity: 5
},
{
type: 'mace',
name: 'hammer of kromzek kings',
rarity: 1
},
{
type: 'sword',
name: 'split blade of thunder',
rarity: 2
},
{
type: 'sword',
name: 'blade of carnage',
rarity: 5
},
]
const getWeapons = (query = {}) => {
let filtered = [];
let constraints = [];
// We could build this object dynamically but I just wanted
// to demonstrate it using your current approach
if (query.hasOwnProperty('type')) {
constraints.push({
name: 'type',
value: query.type
})
}
if (query.hasOwnProperty('rarity')) {
constraints.push({
name: 'rarity',
value: query.rarity
})
}
// Compare all of the conditions and only return weapons
// that match all of the conditions passed.
filtered = weapons.filter(w => {
let matches = 0
constraints.forEach(c => {
if (w[c.name] === c.value) {
matches += 1
}
})
// ensures we only return complete matches
return matches === constraints.length
});
return filtered
}
console.log(getWeapons({
type: 'sword',
rarity: 5
}))
Create an object which has the same property keys as the filters you want to use. Assign a function to each property where the evaluation for that specific filter is specified.
const filters = {
type: (weapon, type) => formatName(weapon.weaponType) === formatName(type),
rarity: (weapon, rarity) => weapon.rarity === rarity,
};
Then loop over the weapons with filter. Inside the filter loop, loop over the keys of the query variable with the every method. This method will return true or false based on if every evaluation is true or not.
In the every loop, use the keys of the query to select the filter from the filters list. Pass the weapon and the values of the query object to these filter functions and return result.
By doing this you can use one, two or no filters at all. And any new filters can be added in the filters object.
const filteredWeapons = weapons.filter((weapon) =>
Object.keys(query).every((filterKey) => {
if (!(filterKey in filters)) {
return false;
}
const filter = filters[filterKey]
const value = query[filterKey]
return filter(weapon, value);
})
);
res.status(HttpStatusCodes.ACCEPTED).send(filteredWeapons);
I am receiving a json response from an API call. I need to store its keys, and create an array of an object. I am intending to this array of an object is created dynamically no matter the keys of the response.
I've already got the keys like this:
const json_getAllKeys = data => {
const keys = data.reduce((keys, obj) => (
keys.concat(Object.keys(obj).filter(key => (
keys.indexOf(key) === -1))
)
), [])
return keys
}
That returned an array (using a sample json):
['name','username', 'email']
But I am trying to use that array to create an array of object that looks like this one
[
{
name: "name",
username: "username",
email: "Email",
}
];
I've been trying mapping the array, but got multiple objects because of the loop, and I need a single one to make it work.
keys.map(i=>({i:i}))
[
{ i: 'id' },
{ i: 'name' },
{ i: 'username' },
{ i: 'email' }
]
Any hint would be useful!
Thanks in advance :D
What you're looking for is Object.fromEntries, which is ECMA2019, I believe, so available in Node >=14 and will be provided as a polyfill if you employ babel.
I can't quite discern what your reduce should produce, but given the sample input, I would write
const input = ['name','username', 'email'];
const result = Object.fromEntries(input.map(name => ([name, name])));
// result == { name: 'name', username: 'username', email: 'email' }
You're definitely on the right track. One thing to remember is the map function will return the SAME number of output as input. So in your example, an array of 3 returns an array of 3 items.
For this reason, map alone is not going to give you what you want. You may be able to map => reduce it. However, here is a way using forEach instead. This isn't a strictly functional programming style solution, but is pretty straight forward and depending on use case, probably good enough.
let keys = ['name','username', 'email'] //you have this array
const obj = {}; // empty object to hold result
keys.forEach(i => {
obj[i] = i; // set the object as you want
})
console.log(obj); // log out the mutated object
// { name: 'name', username: 'username', email: 'email' }
This is in the context of a node express route. I receive a get request with a query param that is a list of IDs. Now I need to make a call-out for each ID and store the result of the callout in an array or object. Each element of the first array (containing the IDs) need to be mapped to its corresponding result from the call-out. I don't have a way to modify the endpoint that I'm hitting from this route so I have to make single calls for each ID. I've done some research and so far I have a mixture of code and sudo code like this:
const ids = req.query.ids;
const idMembers = Promise.all(ids.map(async id => {
// here I'd like to create a single object or associative array
[ id: await callout(id); ]
}));
When all promises resolved I need the final result of idMembers to be like: (The response will be an object with nested arrays and objects I've just simplified it for this post but I need to grab that from the res.payload)
{
'211405': { name: 'name1', email: 'email1#test.co' },
'441120': { name: 'name2', email: 'email2#test.co' },
'105020': { name: 'name3', email: 'email4#test.co' }
}
Oh and of course I need to handle the callout and the promise failures and that's when my lack of experience with javascript becomes a real issue. I appreciate your help in advance!!
Some extra thought I'm having is that I'd have to map the results of the resolved promises to their id and then in a separate iteration I can then create my final array/object that maps the ids to the actual payloads that contain the object. This is still not answering any of my questions though. I'm just trying to provide as much information as I've gathered and thought of.
Promise.all returns an array of results (one item per each promise).
Having this temporary structure it is possible to build the needed object.
const arrayOfMembers = Promise.all(ids.map(async id => {
// ...
return { id, value: await callout(id) } // short syntax for { id: id, value: ... } (see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Object_initializer)
}));
// arrayOfMembers = [
// { id: 211405, value: { name: 'name1', email: 'email1#test.co' } },
// ...
// ]
In pure JS it can be done with for loop or .forEach() call to iterate:
const res = {};
arrayOfMembers.forEach(el => {
const { id, value } = el;
res[el] = value;
});
or by using a single reduce() call
const res = arrayOfMembers.reduce((accumulator, el) => {
const { id, value } = el;
return { ...accumulator, [id]: value };
}, {});
in both cases res will be:
// res = {
// '211405': { name: 'name1', email: 'email1#test.co' },
// ...
// }
P.S.
There is a handy library called lodash. It has tons of small methods for data manipulation.
For example, _.fromPairs() can build an object from [[key1, value1], [key2, value2]] pairs.
As you mentioned you have lodash, so I think the following should work:
const arrayOfKeyValuePairs = Promise.all(ids.map(async id => {
// ...
return [ id, await callout(id) ] // array here so it matches what fromPairs needs
}));
const res = _.fromPairs(arrayOfKeyValuePairs);
I have an object that looks like the following:
let responseData = [
{
"name": "name",
"other": "value",
"anotherField": "blue",
"appRoles": [
{
"code": "roleOne",
"shouldDisplay": true
},
{
"code": "roleTwo",
"shouldDisplay": false
}
]
}
I need to maintain the original structure all while keeping existing properties. I only want to remove/filter out any "appRoles" where "shouldDisplay" is false.
The following works, using a forEach and a filter operation to create a new object array, but is it possible to condense this even more?
let filteredApps;
responseData.forEach((team) => {
let indyTeam = team;
indyTeam.appRoles = team.appRoles.filter((role) => role.shouldDisplay === true);
filteredApps.push(indyTeam);
});
When I use the map operation, I only get an array of the filtered appRoles - missing extra properties on each object such as "name":
let enabledAppRolesOnly =
responseData.map((team) =>
team.appRoles.filter((role) => role.shouldDisplay === true));
array.map function calls a callback for each element of your array, and then push the return value of it to a new array.
from MDN doc:
map calls a provided callback function once for each element in an array, in order, and constructs a new array from the results. callback is invoked only for indexes of the array which have assigned values, including undefined. It is not called for missing elements of the array (that is, indexes that have never been set, which have been deleted or which have never been assigned a value).
So in your case, since you return team.appRoles.filter((role) => role.displayByDefault === true) which is your team array, you only get this.
What you could do would be this (in order to fully clone the object):
let responseData = [{
"name": "name",
"appRoles": [
{
"code": "roleOne",
"shouldDisplay": true
},
{
"code": "roleTwo",
"shouldDisplay": false
}
]
}]
let enabledAppRolesOnly = responseData.map(team => {
const appRoles = team.appRoles.filter(role => role.shouldDisplay === true)
return Object.assign({}, team, { appRoles })
});
console.log(enabledAppRolesOnly)
This will achieve your objective non-destructively. It will build a new array for you.
let responseData = [{
name: "name",
appRoles: [{
code: "roleOne",
shouldDisplay: true
}, {
code: "roleTwo",
shouldDisplay: false
}]
}];
let output = responseData.map(o => Object.assign({}, o, {
appRoles: o.appRoles.filter(r => r.shouldDisplay)
}));
console.log(responseData);
console.log(output);
Code explanation -
map
The map function iterates over the whole array and modifying the each item as specified this should be self evident.
Object.assign
This could be the tricky part -
o=>Object.assign({}, o, {appRoles: o.appRoles.filter(r=>r.shouldDisplay)})
From the docs Object.assign is used to copy values from the object.
The first argument {} causes a new object to be created.
The second argument o causes all props from the object o to be copied in the newly created object.
Now, note that we need to modify the appRoles property and keep only those roles which have shouldDisplay as true. That's exactly what the third argument does. It modifies the appRoles property and gives it the new value.
filter
Now the code -
o.appRoles.filter(r=>r.shouldDisplay)
should not be too difficult.
Here we keep only those roles which meet our criterion (namely shouldDisplay should be true)
If you look at the filter function, it expects the callback value to return a boolean value on whose basis it determines whether value has to be kept or not.
So the following code is not even required,
o.appRoles.filter(r=>r.shouldDisplay===true)
This is enough,
o.appRoles.filter(r=>r.shouldDisplay)
There's some missing information in the question. I'll assume the following:
filteredApps should only contain items where there's at least one appRole for display
it is OK if responseData and filteredApps contains references to the same team objects
there are no other references to team objects that need to keep the original data unaffected
As such, you can reduce your code down to this:
let filteredApps = responseData.filter(team =>
(team.appRoles = team.appRoles.filter(role => role.shouldDisplay)).length;
);
The result will be that each team will have only the .shouldDisplay members in its appRoles, and filteredApps will only have teams with at least one appRole with shouldDisplay being true.
You could build a new array with only part who are valid chinldren elements.
let responseData = [{ name: "name", appRoles: [{ code: "roleOne", shouldDisplay: true }, { code: "roleTwo", shouldDisplay: false }] }],
result = responseData.reduce((r, a) => {
var t = a.appRoles.filter(o => o.shouldDisplay);
if (t.length) {
r.push(Object.assign({}, a, { appRoles: t }));
}
return r;
}, []);
console.log(result);
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