init javascript object with array property with child objects - javascript

Is there a way to initialize a javascript object with an array of child objects in one line? How can I do the following in just on initialization line.
var obj = {doc: 100,
defaultrateid: 32,
rates: [],
};
obj.rates[31] = {rate: 101.00, name: "Rate 1"};
obj.rates[32] = {rate: 121.00, name: "Rate 2"};
Basically what I want is a single javascript object that has my user parameters. This object will be reused on multiple web forms. In the case of 'rates', the forms will have a dropdown to select a rate. The web forms have client side calculations that require the matching rate object based on the rate's unique id (e.g. 32).
I'm trying to use a associative array instead of having to do looping for finding a match based on unique value.

Seems a bit hacky:
obj = {
doc: 100,
defaultrateid: 32,
rates: (new Array(30)).concat([{
rate: 101.00,
name: "Rate 1"
}, {
rate: 121.00,
name: "Rate 2"
}])
};
EDIT:
Maybe you don't really need an array, you can use an object like this:
obj = {
doc: 100,
defaultrateid: 32,
rates: {
"31": {
rate: 101.00,
name: "Rate 1"
},
"32": {
rate: 121.00,
name: "Rate 2"
}
}
};
And you can still get the rates like obj.rates[31].

Do you mean like this?
var obj = {
doc: 100,
defaultrateid: 32,
rates: [{
rate: 101.00
}, {
rate: 121.00
}],
};
alert(obj.rates[1].rate);

Related

Functional Programming exercise I can't figure out

I've been looking at a problem for hours and failing to find a solution. I'm given an array of customer objects.
In each customer object is an array of friends.
In the array of friends is an object for each friend, containing some data, including a name key/value pair.
What I'm trying to solve for: I'm given this customers array and a customer's name. I need to create a function to find if this customer name is in any other customer's friend lists, and if so, return an array of those customer's names.
Below is a customer list. And as an example, one of the customers is Olga Newton. What the code should be doing is seeing that Olga Newton is a customer and is also in the friends lists of Regina and Jay, and should be returning an array of Regina and Jay.
I thought I could do this simply with a filter function, but because the friends list is an array with more objects, this is adding level of complexity for me I can't figure out.
Below is a customer array. The out put should be
['Regina', 'Jay']
and what I've gotten has either been
[{fullCustomerObj1}, {fullCustomerObj2}]
or
[ ]
What am I missing?
Here is the customer array:
var customers = [{
name: "Olga Newton",
age: 43,
balance: "$3,400",
friends: [{
id: 0,
name: "Justice Lara"
}, {
id: 1,
name: "Duke Patrick"
}, {
id: 2,
name: "Herring Hull"
}, {
id: 3,
name: "Johnnie Berg"
}]
}, {
name: "Regina",
age: 53,
balance: "$4,000",
friends: [{
id: 0,
name: "Cheryl Kent"
}, {
id: 1,
name: "Cynthia Wells"
}, {
id: 2,
name: "Gutierrez Waters"
}, {
id: 3,
name: "Olga Newton"
}]
}, {
name: "Jay",
age: 28,
balance: "$3,000",
friends: [{
id: 0,
name: "Cross Barnett"
}, {
id: 1,
name: "Raquel Haney"
}, {
id: 2,
name: "Olga Newton"
}, {
id: 3,
name: "Shelly Walton"
}]
}];
Use filter and map, please.
function friends(c, name){
return c.filter((a) => {
return a.friends.map(b => b.name).includes(name)
}).map(a => a.name);
}
console.log(friends(customers, "Olga Newton"));
// ['Regina', 'Jay']
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/filter
We look to an array (friends[]) inside anther (customers[]), So used two for loops, the first determine witch customer will look for his friends, and the second the array will search inside, then set if statement if the cust name is inside friends[]: adding the customer name to customerFriends[] array, At the end return the customerFriends[].
let cust = "Olga Newton"; // Get the customer name who you look for his friends.
const findFriend = (cust, arrs) => { // Create findFriend function.
let customerFriends = []; // Create an array to set the result to it.
for (let i = 0; i < arrs.length; i++) { // For each Customer.
for (const arr of arrs[i].friends) { // For each Friend.
if (arr.name === cust) { // Use Strict equality to find Customer name in friends[].
customerFriends.push(arrs[i].name); // Add the customer name to the customerFriends[].
}
}
}
return customerFriends;// Return the final results.
}
console.log(findFriend(cust, customers)); // Call the function.

Populating a react-table with an object instead of a list

The documentation for the react-table library (https://github.com/react-tools/react-table#data) states:
"Simply pass the data prop anything that resembles an array or object."
However, the tables are rendered as expected when passing in an array of data, but when passing an object, I get the error:
"Invalid prop data of type object supplied to ReactTable, expected array."
An example data object looks like this:
const data = {
"entry1": {
name: 'Tanner Linsley',
age: 26,
friend: {
name: 'Jason Maurer',
age: 23,
}
}, "entry2": {
name: 'aTanner Linsley',
age: 26,
friend: {
name: 'aJason Maurer',
age: 23,
}
} };
Is this a problem with the structure of my object, or does it simply mean the library does not support the population via objects in this way?
Note: I prefer to maintain this data structure (which will become huge) as an object (dictionary) instead of an array so I can efficiently access elements by key for another use (outside of react-table).
The react-table library would expect an input like that:
const data = [{
name: 'Tanner Linsley',
age: 26,
friend: {
name: 'Jason Maurer',
age: 23,
}
},{
name: 'aTanner Linsley',
age: 26,
friend: {
name: 'aJason Maurer',
age: 23,
}
}];
I prefer to maintain this data structure
Is there any particular reason to that? However, if you really want to do it like that, you could apply the Object.values(...) (MDN Source) method to your data before passing it to the component. In that case you can manage it as you desire and the component will get the right data structure.
const convertedObject = Object.values(data);
But keep in mind that in this case, you will lose your keys entry1 and so on.

Find and update value in array of nested objects

I have an object array as follows:
products = [
{
id: 1,
title: "Product 1",
specifications: {
price: 1.55,
discount: 15,
attributes: [
{
l1: 100,
l2: 80
height:200,
weight: 15,
parameters: [
{
id: 199199 // this is how I identify the parameter
size: 185 // this is what I want to change
}, ...
]
}, ...
]
}
}, ...
]
... and an array of changes to parameters I want to apply, for example: change size to 189 where product.specifications.attributes.parameters.id == 199199.
I'd like to do this without flattening any elements as they are part of a Vue.js data structure, it will break the reactivity.
How could I do this? I am open to using Underscore or lo-dash
This looks ugly, but it is effective:
To make it more dynamic, let's use variables: identifier will be your '199199' value and new_size for the '189' value.
methods: {
updateRecord: function(identifier, new_size) {
this.products.map(function(product) {
product.specifications.attributes.map(function(attribute) {
attribute.parameters.map(function(parameter) {
if (parameter.id == identifier) parameter.size = new_size;
})
});
});
}
}
Here is a working fiddle: https://jsfiddle.net/crabbly/eL7et9e8/
_.forEach(products, function(product) {
_.forEach(_.get(product, 'specifications.attributes', []), function(attribute) {
_.set(_.find(attribute.parameters, {id: 199199}), 'size', 189);
});
});
I believe what you want is underscore's findIndex() - http://underscorejs.org/#findIndex. Once you find which element in the array you want to apply the changes to (comparing the nested id to what you are looking for) you can then make the change to that particular element.

Angularjs - Fetch object in ng-repeat

I have 2 separate json objects coming from the server. Json A below is of a Car model object which is fetch when looking at a car. Json B is meta data which is used throughout the whole application when the web page first loads.
What I need to do is have a lookup on wheel_id while doing a ng-repeat on wheel_handlers so it returns the wheel object from json B and then I can use this within the view and print the results. I think I need to do something with the ng-repeat but I'm not sure to be honest.
A - Car model
[{
id: 14,
name: "Audi",
wheel_handlers: [
{
id: 9,
wheel_id: 62,
arguments: {
amount: 10
}
}
]
}]
B - wheel
{
id: 62,
name: "Change Wheel Size",
arguments: [
{
id: 25,
description: "amount"
}
]
}
I am assuming the following: The Json "A" may include several cars, but also several wheel_handlers (because there is an array at wheel_handler). So the JSON for the cars may also look like this:
[
{
id: 14,
name: "Audi",
wheel_handlers: [
{
id: 9,
wheel_id: 62,
arguments: {
amount: 10
}
},
{
id: 12,
wheel_id: 65,
arguments: {
amount: 12
}
},
{
id: 15,
wheel_id: 30,
arguments: {
amount: 8
}
}
]
},
{
id: 16,
name: "Mercedes",
wheel_handlers: [
{
id: 9,
wheel_id: 62,
arguments: {
amount: 10
}
},
{
id: 12,
wheel_id: 65,
arguments: {
amount: 12
}
}
]
}
]
For the JSON file B I assume that you also meant an Array, which could contain several wheel definitions. As an example:
[
{
id: 62,
name: "Change Wheel Size",
arguments: [
{
id: 25,
description: "amount"
}
]
},
{
id: 65,
name: "test wheel",
arguments: [
{
id: 25,
description: "amount"
}
]
},
{
id: 30,
name: "another wheel",
arguments: [
{
id: 25,
description: "amount"
}
]
}
]
If this is the case, you could iterate over the cars and while iterating call a helper function in the AngularJS controller. You call this helper function and give wheel_handlers of the current car as a parameter. This helper function then checks the wheel_id of each wheel_handler entry and searches these ids in the JSON b file - the wheel definitions. The helper function returns an array containing the wheels, so in the view you may iterate over the wheels. This will use a nested ng-repeat, because at first you iterate over the cars and while iterating over the cars you will iterate over the wheels.
Here is an example of the controller part. I used $scope.cars as the JSON A, and $scope.wheels as JSON B.
var testApp = angular.module('testApp', []);
testApp.controller('testContr', function ($scope) {
$scope.cars = [];
$scope.wheels = [];
$scope.getWheelsByIds = function (wheel_handlers) {
var wheelIds = [];
var returnArray = [];
for (var wheelKey in wheel_handlers) {
wheelIds.push(wheel_handlers[wheelKey].wheel_id);
}
for (var key in $scope.wheels) {
console.log(wheelIds.indexOf($scope.wheels[key].id));
if (wheelIds.indexOf($scope.wheels[key].id) > -1) {
returnArray.push($scope.wheels[key]);
}
}
return returnArray;
}
});
The necessary HTML part could look like this:
<div ng-app="testApp" ng-controller="testContr">
<div ng-repeat="car in cars" ng-init="wheels = getWheelsByIds(car.wheel_handlers)">
<span>Car name: {{car.name}}</span><br/>
<div ng-repeat="wheel in wheels">
<span>Wheel name: {{wheel.name}}</span><br/>
</div>
<br/>
<br/>
</div>
</div>
I create a fiddle demonstration with the test data, view it here: http://jsfiddle.net/4F3YD/10/
You can nest ng-repeats like that, although I'm not sure what you want to achieve
following code will repeat through cars, then wheels in cars and display wheels from object B(wheels) that match the car wheel id, hope that makes sense
<div ng-repeat="car in CarModels">
<div ng-repeat="wheel in car.wheel_handlers">
{{Wheels | filter:wheel.wheel_id}}
</div>
</div>
You can make use of angular filter over here. In the filter function you can check for the id in the second json.
More Documentation on Angular Filter
Code Example:
<div ng-repeat="element in wheel | filterIds:element.id">
And filter Function:
.filter('filterIds', function () {
return function(id) {
$scope.carModel.forEach(function(car){
if(id == car.id)
return id;
});
}
})

What are the reduceAdd, reduceSum , reduceRemove functions in crossfilter? How should they be used?

Can someone explain in simple terms how reduce function with its arguments reduceAdd, reduceSum, reduceRemove works in crossfilter?
Remember that map reduce reduces a dataset by keys of a particular dimension. For example lets use a crossfilter instance with records:
[
{ name: "Gates", age: 57, worth: 72000000000, gender: "m" },
{ name: "Buffet", age: 59, worth: 58000000000, gender: "m" },
{ name: "Winfrey", age: 83, worth: 2900000000, gender: "f" },
{ name: "Bloomberg", age: 71, worth: 31000000000, gender: "m" },
{ name: "Walton", age: 64, worth: 33000000000, gender: "f" },
]
and dimensions name, age, worth, and gender. We will reduce the gender dimension using the reduce method.
First we define the reduceAdd, reduceRemove, and reduceInitial callback methods.
reduceInitial returns an object with the form of the reduced object and the initial values. It takes no parameters.
function reduceInitial() {
return {
worth: 0,
count: 0
};
}
reduceAdd defines what happens when a record is being 'filtered into' the reduced object for a particular key. The first parameter is a transient instance of the reduced object. The second object is the current record. The method will return the augmented transient reduced object.
function reduceAdd(p, v) {
p.worth = p.worth + v.worth;
p.count = p.count + 1;
return p;
}
reduceRemove does the opposite of reduceAdd (at least in this example). It takes the same parameters as reduceAdd. It is needed because group reduces are updated as records are filtered and sometimes records need to be removed from a previously computed group reduction.
function reduceRemove(p, v) {
p.worth = p.worth - v.worth;
p.count = p.count - 1;
return p;
}
Invoking the reduce method would look like this:
mycf.dimensions.gender.reduce(reduceAdd, reduceRemove, reduceInitial)
To take a peek at the reduced values, use the all method. To see the top n values use the top(n) method.
mycf.dimensions.gender.reduce(reduceAdd, reduceRemove, reduceInitial).all()
The returned array would (should) look like:
[
{ key: "m", value: { worth: 161000000000, count: 3 } },
{ key: "f", value: { worth: 35000000000, count: 2 } },
]
The goals of reducing a dataset is to derive a new dataset by first grouping records by common keys, then reducing a dimension those groupings into a single value for each key. In this case we grouped by gender and reduced the worth dimension of that grouping by adding the values of records that shared the same key.
The other reduceX methods are convience methods for the reduce method.
For this example reduceSum would be the most appropriate replacement.
mycf.dimensions.gender.reduceSum(function(d) {
return d.worth;
});
Invoking all on the returned grouping would (should) look like:
[
{ key: "m", value: 161000000000 },
{ key: "f", value: 35000000000 },
]
reduceCount will count records
mycf.dimensions.gender.reduceCount();
Invoking all on the returned grouping would (should) look like:
[
{ key: "m", value: 3 },
{ key: "f", value: 2 },
]
Hope this helps :)
Source: https://github.com/square/crossfilter/wiki/API-Reference
http://blog.rusty.io/2012/09/17/crossfilter-tutorial/
var livingThings = crossfilter([
// Fact data.
{ name: “Rusty”, type: “human”, legs: 2 },
{ name: “Alex”, type: “human”, legs: 2 },
{ name: “Lassie”, type: “dog”, legs: 4 },
{ name: “Spot”, type: “dog”, legs: 4 },
{ name: “Polly”, type: “bird”, legs: 2 },
{ name: “Fiona”, type: “plant”, legs: 0 }
]);
For example, how many living things are in my house?
To do this, we’ll call the groupAll convenience function, which selects all
records into a single group, and then the reduceCount function, which
creates a count of the records.
// How many living things are in my house?
var n = livingThings.groupAll().reduceCount().value();
console.log("There are " + n + " living things in my house.") // 6
Now let’s get a count of all the legs in my house. Again, we’ll use the groupAll function to get all records in a single group, but then we call the
reduceSum function. This is going to sum values together. What values?
Well, we want legs, so let’s pass a function that extracts and returns the number of legs from the fact.
// How many total legs are in my house?
var legs = livingThings.groupAll().reduceSum(function(fact) {
return fact.legs;
}).value()
console.log("There are " + legs + " legs in my house.")
reduceCount function creates a count of the records.
reduceSum function is the sum values of these records.

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