const aboutMe = [{
"name": "frank",
"about": [{
"mood": "happy",
"dinner": [{
"first": "desert",
"last": "noodles"
}]
},
{
"mood": "happy",
"dinner": [{
"first": "desert",
"last": "noodles"
}]
},
{
"mood": "happy",
"dinner": []
}
]
}]
const AllBreak = aboutMe.about.map((dinner) => ((dinner.first, dinner.last)));
const expectedOutput =["first": "desert", "last": "noodles", "first": "desert", "last": "noodles"]
console.log(aboutMe, AllBreak, expectedOutput)
so am trying to filter through a nested array learning from a tutorial I don't know why it returns cannot read property of map why is that pretty sure i filtered correctly according to the tutorial
Firstly, aboutMe is an array with an object that has an about property in it. So, if you want to access this property, you need to first access the first element of the array and then access the about property in it.
Secondly, (dinner.first, dinner.second) doesn't actually make any sense here.
Because when you have multiple expressions separated by commas in a bracket, each of those expressions get evaluated but only the last one is returned. So, here returning (dinner.first, dinner.second) is equivalent to returning dinner.second.
So, if you only want dinner.second then just return that or put them in an array (or object) and return that.
Also, since in your example it seems that it is not guaranteed that the dinner array would always have an object inside it, it is best to use Optional Chaining here.
Please have look at the solution below:
const
aboutMe = [{name:"frank",about:[{mood:"happy",dinner:[{first:"desert",last:"noodles"}]},{mood:"happy",dinner:[{first:"desert",last:"noodles"}]},{mood:"happy",dinner:[]}]}],
res = aboutMe[0].about.map(({dinner}) => [dinner?.[0]?.first, dinner?.[0]?.last])
console.log(res);
aboutMe is an array, if you want to get the property of the first element, you can use indexing [0]
const AllBreak = aboutMe[0].about.map(() => ...);
Related
I have a JSON file with order data. The JSON file is formatted like this:
{
"orders": [
{"name": "Peter", "email": "peter#aol.com"}
{"name": "David", "email": "david#aol.com"}
{ "name": "George", "email": "george#aol.com"}
]
}
As you can see; all the data is part of a branch called "orders" and then each order is its own branch, but the branch doesn't have a name.
I am trying to generate a list of the "name"s in the dataset.
With a simplified dataset, I would do something like:
$(data).each(function(i, name){
$('#namesText').append($("li")
.append($("li").append(name.name))
});
})
This however doesn't work as the data is not in the first level of the tree.
My question is, how do I go down levels when the levels don't have a name?
This sounds like a DFS problem where each object has keys that can possibly be a primitive data type or another object. Since the name field could be at any level in this given constraint you need to solve for, I would say use DFS algo where it traverses each key in the object and if there is another object, look into that until you find a name field. Better solution is to redesign the data structure so that you are guaranteed to know which level and location the name field is at any time.
If you want a list of the name property from the elements of the orders array you could use Array.map:
const names = myJson.orders.map(o => o.name);
Try
namesText.innerHTML= data.orders.map(p=>`<li>${escape(p.name)}</li>`).join``
var data = {
"orders": [
{
"name": "Peter",
"email": "peter#aol.com",
},
{
"name": "David",
"email": "david#aol.com",
},
{
"name": "George",
"email": "george#aol.com",
}
]
}
namesText.innerHTML= data.orders.map(p=>`<li>${escape(p.name)}</li>`).join``
<ul id="namesText"></ul>
I would like to be able to type in "Hammerhead" to call the "Hammerhead Shark" object without its full name. Is this possible and if so how?
I tried using array.indexOf(string) though it doesn't really seem to help since it requires an exact match such as typing "Hammerhead Shark"
JS:
const JSON = require('animals.json');
var animals = Object.keys(JSON);
if (animals.indexOf("Hammerhead")) {
console.log(JSON["Hammerhead"].name);
}
JSON:
{
"Hammerhead Shark": {
"name": "Shark",
"age": "300"
},
"Duck": {
"name": "Duck",
"age": "1000"
}
}
I expect the output to be "Shark" instead of undefined.
It seems you want to get access the value in object. By its partial name.
Get the entries of object using Object.entries()
Find the key which includes() the given partial key.
return the second element of the found entry.
const obj = { "Hammerhead Shark": { "name": "Shark", "age": "300" }, "Duck": { "name": "Duck", "age": "1000" } }
function getValueByPartialKey(obj,key){
return (Object.entries(obj).find(([k,v]) => k.includes(key)) || [])[1]
}
console.log(getValueByPartialKey(obj,"Hammerhead"))
You can use string.includes(word) to return the name that matches the string that you're searching for, along with Array.filter iterates over the values too, and returns the result(s) you want.
I have an array of objects, where inside each object I have another array. I need to access the object inside that array. How do I do that?
As an example, here is my function where I log into the console each one of those arrays. And I want to console log each description instead.
const var = data.filter((u) => {
console.log(u.array)
})
And here is the JSON data
[
{
"agreed": true,
"email": "test#test.com"
"array": [
{
"name": "Alex",
"city": "Pedro",
"state": "WA",
"description": "Alex was very patient. He is one of the good guys!"
}
]
}
]
Here is the code snippet. data contains the original array then u contains each object of outer array. Then u.array.map traverses each individual array and i.description contains each sub-array's description.
data.map((u) => {
u.array.map((i) => {
console.log(i.description);
}
})
if you know the exact index, you can do this.
const var = data.filter((u) => {
console.log(u.array[0].description)
})
if you dont know the exact index, or if you wanna do this for each item in the array you can do this.
const var = data.filter((u) => {
u.array.forEach(item => {
console.log(item.description)
})
})
Well,
if this would be the structure of your Javascript Object
var data =
[
{
"agreed": true,
"email": "test#test.com"
"array": [
{
"name": "Alex",
"city": "Pedro",
"state": "WA",
"description": "Alex was very patient. He is one of the good guys!"
}
]
}
]
Then You can access the array by,
data[0].array[0].name;
And you can console.log description like this, if you are using jquery
$.each(data[0].array, function(i,v){
console.log(v.description);
})
You index into arrays with array[someIndex] starting with 0 for the first item.
So you can:
let arr = [{
"agreed": true,
"email": "test#test.com",
"array": [{
"name": "Alex",
"city": "Pedro",
"state": "WA",
"description": "Alex was very patient. He is one of the good guys!"
}]
}]
// get the first whole object
console.log(arr[0])
// get the arra property of the first object
console.log(arr[0].array)
// get the first object of that array
console.log(arr[0].array[0])
// get a property on that object
console.log(arr[0].array[0].name)
If you need to dig into an array and access of manipulate values, you can use tools like forEach, reduce(), etc. to loop over them:
let arr = [{"agreed": true,"email": "test#test.com","array": [{"name": "Alex","city": "Pedro","state": "WA","description": "Alex was very patient. He is one of the good guys!"},{"name": "Mark","city": "Anchorage","state": "AK","description": "Mark is also patient. He is one of the good guys!"}]},{"agreed": true,"email": "test#test.com","array": [{"name": "Steve","city": "New York","state": "NY","description": "Steve was very patient. He is one of the good guys!"},{"name": "Nancy","city": "Anchorage","state": "AK","description": "Nancy is also patient. She is awesome!"}]}]
// log each name
arr.forEach(obj => {
obj.array.forEach(item => {
console.log(item.name)
})
})
// build a new list of just the cities
let cities = arr.reduce((arr, obj) => {
obj.array.forEach(item => {
arr.push(item.city)
})
return arr
}, [])
console.log(cities)
You can save all descriptions to an array or just display it, like this
let descriptions = [];
data.map(item => item.array)
.forEach(array => {
array.forEach(obj => {
console.log(obj.description);
descriptions.push(obj.description);
});
});
console.log(descriptions);
I wanted to know if there is some performance issue related in the two below coding paradigms. Which one is the best and why?
var data = [{
"name": "ABC",
"code": 1,
"age": 97
},{
"name": "XYZ",
"code": 12,
"age": 12
},{
"name": "LMN",
"code": 121,
"age": 172
}
];
var response = [];
Method1
data.forEach(function(entry){
var obj = {
"NAME": entry["name"],
"AGE": entry["age"]
};
response.push(obj);
});
Method2
data.forEach(function(entry){
var obj = {};
obj["NAME"] = entry["name"];
obj["AGE"] = entry["age"];
response.push(obj);
});
For output object, I need say suppose, only 10 keys out of 100 keys
The object has many keys in it. Only limited are shown in the example. Which coding standard to choose and why? Please, can anybody explain?
No need to create the objects and then make a Array.prototype.push() for everly loop iteration...
You can directly use Array.prototype.map() instead of Array.prototype.forEach() and better access the object property values by the dot notation:
const data = [{
"name": "ABC",
"code": 1,
"age": 97
},{
"name": "XYZ",
"code": 12,
"age": 12
},{
"name": "LMN",
"code": 121,
"age": 172
}
];
const response = data.map(obj => ({
NAME: obj.name,
AGE: obj.age
}));
console.log(response)
Both approaches are fine and one should not be "faster" than the other, at least not enough to justify using the other one. Use the one you like.
But, if you're still looking for closure. The first one should be faster since it defines the entire object all at one go. There's no "look-ups" the engine have to do. It's all done at one go.
On a separate note, consider using the dot notation, it should be faster since the engine will not have to create strings. So, change
entry["name"]
to
entry.name
Also, if this is your actual code and the purpose is to modify the result to have just name and age and no code. You can do
data.forEach(user => delete user.code)
I am trying to use underscoreJs to manipulate a JavaScript object and having problems doing so.
Here is my example
var data = {
"label": "SomeName",
"parent": [{
"id": "parentId",
"resources": [{
"name": "ID1NAME",
"calls": [
"user_get", "user2_post", "user3_delete"
]
}, {
"name": "ID2",
"calls": [
"employee1_get", "employee2_delete", "employee3_update"
]
}]
}]
};
var res = _(data).chain().
pluck('parent').
flatten().
findWhere(function(item){
item === "user_get"
}).
value();
console.log(res);
Using an element which is a part of data.parent.calls[] (example : "user_get") I would like to extract its parent object, i.e. data.parent[0].
I tried above but always get undefined. I appreciate any help on this.
One of the problems you're having is your use of _.pluck. If you execute _.pluck over an object, it'll go over the keys of the object trying to retrieve the property you specified as the second argument (in this case, 'parent'). 'label' is a string and 'parent' is an array so thus the array that you get as a result is [undefined, undefined]. The rest will then go wrong.
One solution could be as follows:
function findCallIndexInParent(call, parent) {
return _.chain(parent)
.pluck('resources')
.flatten()
.findIndex(function (obj) {
return _.contains(obj.calls, call);
})
.value();
}
function findCall(call, data) {
var parent = data.parent;
return parent[findCallIndexInParent(call, parent)];
}
console.log(findCall('user_get', data));
findCall is just a convenient method that will pass the parent property of data to findCallIndexInParent (that will retrieve the index where call is) and return the desired object with the parent array.
Lodash (a fork of underscore) provides a method to get the property of an object that would have come really handy in here (sadly, underscore doesn't have it).
The explanation of findCallIndexInParent is as follows:
Chain the parent list
pluck the resources array
As pluck maps, it returns a list of lists so a flatten is needed.
Find the index of the element which calls contains call
Return the value (the index) of the object that contains call within parent.
Here's the fiddle. Hope it helps.
This would seem to do the trick.
function findByCall(data, call) {
return _.find(data.parent, function(parent) { //From data.parent list, find an item that
return _.some(parent.resources, function(resource) {//has such parent.resource that it
return _.includes(resource.calls, call); //includes the searched resource.calls item
});
});
}
//Test
var data = {
"label": "SomeName",
"parent": [{
"id": "parentId",
"resources": [{
"name": "ID1NAME",
"calls": [
"user_get", "user2_post", "user3_delete"
]
}, {
"name": "ID2",
"calls": [
"employee1_get", "employee2_delete", "employee3_update"
]
}]
}]
};
console.log(findByCall(data, 'user_get'));
<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.3/underscore.js"></script>
If I understand correctly, you want to get the index of the element in the parent array which has any resource with the specified call.
data = {
"label": "SomeName",
"parent": [{
"id": "parentId",
"resources": [{
"name": "ID1NAME",
"calls": [
"user_get", "user2_post", "user3_delete"
]
}, {
"name": "ID2",
"calls": [
"employee1_get", "employee2_delete", "employee3_update"
]
}]
}]
}
// find the index of a parent
const index = _.findIndex(data.parent, parent =>
// that has any (some) resources
_.some(parent.resources, resource =>
// that contains 'user_get' call in its calls list
_.contains(resource.calls, 'user_get')
)
)
console.log(index) // 0
<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.3/underscore-min.js"></script>
If you want to find the actual parent object, use find instead of findIndex
If you want to find all parent objects matching this call, use filter instead of findIndex