JS failing to populate arrays from array

JS failing to populate arrays from array - javascript

I have an array of exam result, it contains the date the exam was sat and the grade achieved. I want to put all the grades in one array and the dates in another so I can plot them in a chart.js application. How can I separte them?
Results Array example layout:
Results{
[0] {examDate: "2017-10-16T10:30:00", <ResultEntry>grade: A}
[1] {examDate: "2017-15-16T11:00:00", <ResultEntry>grade: C}
[2] {examDate: "2017-16-16T11:30:00", <ResultEntry>grade: B}
[3]{examDate: "2017-20-16T12:00:00", <ResultEntry>grade: B}
}
But what I try doesn't populate the two new arrays
var dateArray;
var gradeArray;
var counter = 0;
for (members in results) {
dateArray[counter] = members[0];
gradeArray[counter] = members[1];
counter++;//increment storage index
}
I have Jquery installed on my project can the .each functionality be used to achieve this?

You can use map method by passing a callback function.
The map() method creates a new array with the results of calling a provided function(callback) on every element in the calling array.
let results=[{examDate: "2017-10-16T10:30:00", grade: 'A'},{examDate: "2017-15-16T11:00:00", grade: 'C'},{examDate: "2017-16-16T11:30:00", grade: 'B'},{examDate: "2017-20-16T12:00:00", grade: 'B'}];
let dates=results.map(function(a){
return a.examDate;
});
let grades=results.map(function(a){
return a.grade;
});
console.log(dates);
console.log(grades);
You can use also arrow functions.
let grades=results.map(a => a.grade);

You need to get values of fields from array elements. Check this:
var dateArray = [];
var gradeArray = [];
var counter = 0;
for (var member in results) {
dateArray.push(member.examDate);
gradeArray.push(member.grade);
}

If results is an array, then in this line
for (members in results) {
members is basically the index value 0,1,..
so members[0] will be undefined
I have Jquery installed on my project can the .each functionality be
used to achieve this?
Yes, but why not use the native forEach instead
var dateArray = [], gradeArray = [];
results.forEach( function( result ){
dateArray.push( result.examDate );
gradeArray.push( result.grade );
});

Considering that the results array is has the following shape:
let results = [
{ examDate: "2017-10-16T10:30:00", grade: 'A' },
{ examDate: "2017-15-16T11:00:00", grade: 'C' },
{ examDate: "2017-16-16T11:30:00", grade: 'B' },
{ examDate: "2017-20-16T12:00:00", grade: 'B' }
];
Array.prototype.map is perfect for this purpose:
let dateArray = results.map(result => result.examDate);
let gradeArray = results.map(result => result.grade);
You can also loop over the elements in a few different ways:
let dateArray = [],
gradeArray = [];
for (let result of results) {
dateArray.push(result.examDate);
gradeArray.push(result.grade);
}
And a solution similar to yours:
var dateArray = [],
gradeArray = [];
for (var i = 0; i < results.length; i++) {
dateArray[i] = results[i].examDate;
gradeArray[i] = results[i].grade;
}
You can also push them into the array instead of setting a position to the value:
var dateArray = [],
gradeArray = [];
for (var i = 0; i < results.length; i++) {
dateArray.push(results[i].examDate);
gradeArray.push(results[i].grade);
}
And using jQuery each as you mention:
var dateArray = [],
gradeArray = [];
$.each(results , function(i, value) {
dateArray.push(value.examDate);
gradeArray.push(value.grade);
});

Related

Is there a way to iterate over an Object based upon the length of an array?

I have this array ["12345678", "87654321"]
And I want to inject each index into an object in the itemId category and loop over the object again placing the second index into another itemId category.
var myArray = ["12345678", "87654321", "12345678"]
var idArray =[]
var arrayLength = myArray.length;
for (var i =0; i < arrayLength; i++) {
let idElement = myArray[i]
idArray.push(idElement);
console.log(idElement);
let multipleitems = {
Request: {
Details: {
id: idArray,
amount: 1
},
}
};
Gives me this output
Request: {Details: {Id: ["12345678", "12345678", "12345678" ], amount: 1}}
Is it possible to iterate over "details however many times based upon how many indexes are in myArray to get this output
{"Request":{"Details":[{"Id":"12345678","amount":1},{"itemId":"87654321","amount":1},{"Id":"12345678","amount":1}]}}

This is a very basic array map() operation. You return a new object every iteration and map() itself returns a new array
var myArray = ["12345678", "87654321", "12345678"];
let multipleitems = {
Request: {
Details: myArray.map(id => ({id, amount:1}) )
}
};
console.log(multipleitems)

Making subarrays from an array algorithm javascript [duplicate]

I have a JavaScript array with 8 elements and some elements are repeating. I want to create separate arrays for identical elements.
example:
original array is [1,1,1,3,3,1,2,2]
resulting arrays will be [1,1,1,1],[3,3],[2,2]
I want a function similar to this:
var array=[1,1,1,3,3,1,2,2];
var createNewArrays=function(array){
for (var i = 0; i < array.length; i++) {
for (var j = 0; j < array.length; j++) {
}
}
};

You could use a hash table as reference to the sub arrays for the collection.
var array = [1, 1, 1, 3, 3, 1, 2, 2],
result = [];
array.forEach(function (a) {
a in this || result.push(this[a] = []);
this[a].push(a);
}, Object.create(null));
console.log(result);

var arr = [1,1,1,3,3,1,2,2];
var hash = Object.create(null);
var result = arr.reduce(function(r, n) {
if(!hash[n]) {
hash[n] = [];
r.push(hash[n]);
}
hash[n].push(n);
return r;
}, []);
console.log(result);
And an ES6 solution that uses Map, and spread:
const arr = [1,1,1,3,3,1,2,2];
const result = [...arr.reduce((r, n) =>
r.set(n, (r.get(n) || []).concat(n)),
new Map()).values()];
console.log(result);

Let's assume you want the resulting arrays to be properties on an object keyed by the value they represent. You just loop through the array, creating or adding to the arrays on the object properties as you go:
var array=[1,1,1,3,3,1,2,2];
var result = {};
array.forEach(function(entry) {
(result[entry] = result[entry] || []).push(entry);
});
console.log(result);
That's a bit dense, here's a clearer version:
var array=[1,1,1,3,3,1,2,2];
var result = {};
array.forEach(function(entry) {
var subarray = result[entry];
if (!subarray) {
subarray = result[entry] = [];
}
subarray.push(entry);
});
console.log(result);

Javascript map function to create multiple objects

I need some dummy data that I can use. I usually, manually create my data in a variable like...
const jsonData = [
{
name: 'random',
age: '0',
}
];
I'm trying to create a function that gives me back an array with a list of objects in (like the above) the amount of objects in the array is based on the value I give it.
I came to the conclusion using the map function would be best, like so:
const myMap = new Map();
myMap.forEach((q, n) => {
});
I'm still learning. Honestly now sure how I'd go about creating this.

You can use a simple loop:
function genData(n) {
var results = [];
for (var i = 0; i < n; i++) {
results.push({name: 'random', age: 0});
}
return results;
}
If you want to randomize the property values, look into Math.random.
Here is a simple example that picks a random value from provided lists:
function genData(n, values) {
var results = [];
for (var i = 0; i < n; i++) {
var obj = {};
for (var prop in values) {
obj[prop] = values[prop][Math.floor(Math.random() * values[prop].length)];
results.push(obj);
}
}
return results;
}
console.log(genData(3, {name: ['foo', 'bar', 'baz'], age: [0, 10, 20, 30, 40]}));

array object manipulation to create new object

var actual = [
{"country":"UK","month":"JAN","SR":"John P","AC":"24","PR":"2","TR":1240},
{"country":"AUSTRIA","month":"JAN","SR":"Brad P","AC":"64","PR":"12","TR":1700},
{"country":"ITALY","month":"JAN","SR":"Gim P","AC":"21","PR":"5","TR":900},
{"country":"UK","month":"FEB","SR":"John P","AC":"14","PR":"4","TR":540},
{"country":"AUSTRIA","month":"FEB","SR":"Brad P","AC":"24","PR":"12","TR":1700},
{"country":"ITALY","month":"FEB","SR":"Gim P","AC":"22","PR":"3","TR":600},
{"country":"UK","month":"MAR","SR":"John P","AC":"56","PR":"2","TR":1440},
{"country":"AUSTRIA","month":"MAR","SR":"Brad P","AC":"24","PR":"12","TR":700},
{"country":"ITALY","month":"MAR","SR":"Gim P","AC":"51","PR":"5","TR":200}
];
var expect = [
{month:"JAN",val: {"UK":"24","AUSTRIA":"64","ITALY":"21"}},
{month:"FEB",val: {"UK":"14","AUSTRIA":"24","ITALY":"22"}},
{month:"MAR",val: {"UK":"56","AUSTRIA":"24","ITALY":"51"}}
];
I have array of objects which i need to reshape for one other work. need some manipulation which will convert by one function. I have created plunker https://jsbin.com/himawakaju/edit?html,js,console,output
Main factors are Month, Country and its "AC" value.

Loop through, make an object and than loop through to make your array
var actual = [
{"country":"UK","month":"JAN","SR":"John P","AC":"24","PR":"2","TR":1240},
{"country":"AUSTRIA","month":"JAN","SR":"Brad P","AC":"64","PR":"12","TR":1700},
{"country":"ITALY","month":"JAN","SR":"Gim P","AC":"21","PR":"5","TR":900},
{"country":"UK","month":"FEB","SR":"John P","AC":"14","PR":"4","TR":540},
{"country":"AUSTRIA","month":"FEB","SR":"Brad P","AC":"24","PR":"12","TR":1700},
{"country":"ITALY","month":"FEB","SR":"Gim P","AC":"22","PR":"3","TR":600},
{"country":"UK","month":"MAR","SR":"John P","AC":"56","PR":"2","TR":1440},
{"country":"AUSTRIA","month":"MAR","SR":"Brad P","AC":"24","PR":"12","TR":700},
{"country":"ITALY","month":"MAR","SR":"Gim P","AC":"51","PR":"5","TR":200}
];
var outTemp = {};
actual.forEach(function(obj){ //loop through array
//see if we saw the month already, if not create it
if(!outTemp[obj.month]) outTemp[obj.month] = { month : obj.month, val: {} };
outTemp[obj.month].val[obj.country] = obj.AC; //add the country with value
});
var expected = []; //convert the object to the array format that was expected
for (var p in outTemp) {
expected.push(outTemp[p]);
}
console.log(expected);

Iterate through array and create new list
var actual = [
{"country":"UK","month":"JAN","SR":"John P","AC":"24","PR":"2","TR":1240},
{"country":"AUSTRIA","month":"JAN","SR":"Brad P","AC":"64","PR":"12","TR":1700},
{"country":"ITALY","month":"JAN","SR":"Gim P","AC":"21","PR":"5","TR":900},
{"country":"UK","month":"FEB","SR":"John P","AC":"14","PR":"4","TR":540},
{"country":"AUSTRIA","month":"FEB","SR":"Brad P","AC":"24","PR":"12","TR":1700},
{"country":"ITALY","month":"FEB","SR":"Gim P","AC":"22","PR":"3","TR":600},
{"country":"UK","month":"MAR","SR":"John P","AC":"56","PR":"2","TR":1440},
{"country":"AUSTRIA","month":"MAR","SR":"Brad P","AC":"24","PR":"12","TR":700},
{"country":"ITALY","month":"MAR","SR":"Gim P","AC":"51","PR":"5","TR":200}
];
var newList =[], val;
for(var i=0; i < actual.length; i+=3){
val = {};
val[actual[i].country] = actual[i]["AC"];
val[actual[i+1].country] = actual[i+1]["AC"];
val[actual[i+2].country] = actual[i+2]["AC"];
newList.push({month: actual[i].month, val:val})
}
document.body.innerHTML = JSON.stringify(newList);

This is the correct code... as above solution will help you if there are 3 rows and these will be in same sequnece.
Here is perfect solution :
var actual = [
{"country":"UK","month":"JAN","SR":"John P","AC":"24","PR":"2","TR":1240},
{"country":"AUSTRIA","month":"JAN","SR":"Brad P","AC":"64","PR":"12","TR":1700},
{"country":"ITALY","month":"JAN","SR":"Gim P","AC":"21","PR":"5","TR":900},
{"country":"UK","month":"FEB","SR":"John P","AC":"14","PR":"4","TR":540},
{"country":"AUSTRIA","month":"FEB","SR":"Brad P","AC":"24","PR":"12","TR":1700},
{"country":"ITALY","month":"FEB","SR":"Gim P","AC":"22","PR":"3","TR":600},
{"country":"UK","month":"MAR","SR":"John P","AC":"56","PR":"2","TR":1440},
{"country":"AUSTRIA","month":"MAR","SR":"Brad P","AC":"24","PR":"12","TR":700},
{"country":"ITALY","month":"MAR","SR":"Gim P","AC":"51","PR":"5","TR":200}
];
var tmpArray = [];
var obj =[];
for(var k=0; k<actual.length; k++){
var position = tmpArray.indexOf(actual[k].month);
if(position == -1){
tmpArray.push(actual[k].month);
val = {};
for(var i=0; i<actual.length; i++){
if(actual[i].month == actual[k].month){
val[actual[i].country] = actual[i]["AC"];
}
}
obj.push({month: actual[k].month, val:val});
}
}

Comparing an Array with an Objects' Array in JavaScript

I am new to JavaScript and wondering how can I compare an array with another array consists of JavaScript objects.
The array is a series of sorted time in the "YYYY-MM-DD" format.
The array of objects missed some price values of several days.
I want to find the missed value and assign it as "NULL".
For example, I have an array as:
array = ['2014-10-09','2014-10-10','2014-10-11','2014-10-12'];
and an array with objects as:
objArray = [{
date:"2014-10-09",
price:"100"
},
{
date:"2014-10-10",
price:"99"
},
{
date:"2014-10-12",
price:"102"
}];
I want to get the price array in this way:
priceResult = [100, 99, "NULL", 102];
What would be the most efficient way without using other libraries? I wanted to see if anyone had a more elegant solution. I deeply appreciate your help.

You can create a lookup set from the object array, then you can use that to translate the dates to prices.
This scales well, as it is an O(n+m) solution rather than the O(n*m) solution that you get if you use a loop in a loop to find the prices.
var array = ['2014-10-09','2014-10-10','2014-10-11','2014-10-12'];
var objArray = [{ date:"2014-10-09", model:"A", price:"100" },{ date:"2014-10-10", model:"A", price:"99" },{ date:"2014-10-12", model:"A", price:"102" }];
var lookup = {};
for (var i = 0; i < objArray.length; i++) {
lookup[objArray[i].date] = parseInt(objArray[i].price, 10);
}
var priceResult = [];
for (var i = 0; i < array.length; i++) {
if (lookup.hasOwnProperty(array[i])) {
priceResult.push(lookup[array[i]]);
} else {
priceResult.push('NULL');
}
}
// output result in StackOverflow snippet
document.write(JSON.stringify(priceResult));
Note: Instead of the string 'NULL' you might want to use the value null instead, as it is generally easier to handle.

lodash is the best library for this. But you did say "without using other libraries", so you will need to do it natively.
The easiest way to do it is nested for loops:
var i, j, d, res = [];
for (i=0; i<dateArray.length; i++) {
d = dateArray[i];
for (j=0; j<objArray.length; j++) {
if (objArray[j] && objArray[j].date && objArray[j].date === d) {
res.push(objArray[j].price);
j = objArray.length; // don't waste energy searching any more, since we found it
}
}
}
// res now contains all you wanted
If objArray is really big, and you don't want to search it multiple times, then you could turn it into an object indexed by date:
var i, obj = {}, d, res = [];
for (i=0; i<objArray.length; i++) {
if (objArray[i] && objArray[i].date) {
obj[objArray[i].date] = objArray[i];
}
}
for (i=0; i<dateArray.length; i++) {
d = dateArray[i];
res.push(obj[d] ? obj[d].price : null : null);
}
// res now contains all you wanted

Loop trough the object and search for the date in your array
// Add contains to array proto: http://css-tricks.com/snippets/javascript/javascript-array-contains/
var priceResult = [];
for(var i in objArray) {
if(dateArray.contains(objArray[i].date)) priceResult.push(objArray[i].date));
}
console.log('matches:', priceResult);

This function will give you map of all individual arrays in your object array
function getArrayMap(array) {
var map={}
for(var i=0;i<array.length;i++){
var o = array[i];
for(var k in o){
if(!map[k]){
map[k]=[];
}
map[k].push(o[k]);
}
}
return map;
}
you can use it like -
var map = getArrayMap(objArray);
console.log(map["date"]);//date array
console.log(map["price"]);//price array
console.log(map["model"]);//model array

If i am understanding your question correctly, for all the values in array, you want to check the objArr and find the price for each date, and if not found u want to inset null. If this is what you want, then following will help
var found= false;
var list=[];
for(var i=0; i< dateArray.length; i++)
{
for(var j=0; j< objArray.length; j++)
{
if(objArray[j].date == dateArray[i])
{
list.push(objArray[j].price);
found = true;
}
}
if(!found)
{
list.push("null");
}
found = false;
}
alert(list);

(I'm going to call your first array dates rather than array, to avoid confusion.)
There are basically two options:
Loop through your dates array and, for each entry, loop through the objArray looking for a match, and when found add to your priceResult array, or
Build a map from your objArray, then loop through yourdatesarray once, building thepriceResult` array.
Looping and Looping
You can loop through your dates array using forEach, and you can use Array#some to find out whether your objArray contains the date and add to priceResult if so (it's an ES5 feature, but you can polyfill it for really old browsers):
var priceResult = [];
dates.forEach(function(date) {
objArray.some(function(object) {
if (object.date == date) {
priceResult.push(object.price);
return true;
}
});
});
Array#some keeps looping until you return true, which is why we do that when we find the firs tmatch. That's why I say this is "looping and looping," even though we only write one loop, the other is within Array#some.
var dates = ['2014-10-09', '2014-10-10', '2014-10-11', '2014-10-12'];
var objArray = [
{
date: "2014-10-09",
model: "A",
price: "100"
},
{
date: "2014-10-10",
model: "A",
price: "99"
},
{
date: "2014-10-12",
model: "A",
price: "102"
}
];
// Do it
var priceResult = [];
dates.forEach(function(date) {
objArray.some(function(object) {
if (object.date == date) {
priceResult.push(object.price);
return true;
}
});
});
snippet.log(priceResult.join(", "));
<!-- Script provides the `snippet` object, see http://meta.stackexchange.com/a/242144/134069 -->
<script src="http://tjcrowder.github.io/simple-snippets-console/snippet.js"></script>
Mapping and Looping
First, create a map of prices by date:
var prices = {};
objArray.forEach(function(object) {
prices[object.date] = object.price;
});
...then create your results:
var priceResult = [];
dates.forEach(function(date) {
if (prices.hasOwnProperty(date)) {
priceResult.push(prices[date]);
}
});
var dates = ['2014-10-09', '2014-10-10', '2014-10-11', '2014-10-12'];
var objArray = [
{
date: "2014-10-09",
model: "A",
price: "100"
},
{
date: "2014-10-10",
model: "A",
price: "99"
},
{
date: "2014-10-12",
model: "A",
price: "102"
}
];
// Create the map
var prices = {};
objArray.forEach(function(object) {
prices[object.date] = object.price;
});
// Create your results:
var priceResult = [];
dates.forEach(function(date) {
if (prices.hasOwnProperty(date)) {
priceResult.push(prices[date]);
}
});
// Show them
snippet.log(priceResult.join(", "));
<!-- Script provides the `snippet` object, see http://meta.stackexchange.com/a/242144/134069 -->
<script src="http://tjcrowder.github.io/simple-snippets-console/snippet.js"></script>

var dates = ['2014-10-09','2014-10-10','2014-10-11','2014-10-12'];
var objArray = [{date:"2014-10-09", model:"A", price:"100" }, {date:"2014-10-10", model:"A", price:"99" }, {date:"2014-10-12", model:"A", price:"102" }];
var val;
var priceResult = [];
for (var a in dates) {
val = null;
for (var b in objArray) {
if (dates[a] == objArray[b].date) {
val = objArray[b].price;
}
}
priceResult.push(val);
}
var dates = ['2014-10-09', '2014-10-10', '2014-10-11', '2014-10-12'];
var objArray = [{
date: "2014-10-09",
model: "A",
price: "100"
}, {
date: "2014-10-10",
model: "A",
price: "99"
}, {
date: "2014-10-12",
model: "A",
price: "102"
}];
var val;
var priceResult = [];
for (var a in dates) {
val = null;
for (var b in objArray) {
if (dates[a] == objArray[b].date) {
val = objArray[b].price;
}
}
priceResult.push(val);
}
// output result in StackOverflow snippet
document.write(JSON.stringify(priceResult));

Try this:
var temp[]
temp= jQuery.grep(objArray , function (n, i)
{
for(j=0;j<dateArray.lenght+j++ )
if( n.date === dateArray[j])
return n.price;
);

dateArray = ["2014-10-09", "2014-10-10", "2014-10-11", "2014-10-12"];
function ObjectExample(date1,model,price)
{
this.date1 = date1;
this.model = model;
this.price = price;
}
var objArray = [new ObjectExample("2014-10-09","A","100"), new ObjectExample("2014-10-10","A","99"), new ObjectExample("2014-10-12","A","102")];
var i = 0;
var priceDate = new Array();
var count = 0;
while(i < dateArray.length)
{
var j = 0;
while(j < objArray.length)
{
if(dateArray[i] == objArray[j].date1)
{
priceDate[count] = objArray[j].price;
break;
}
else priceDate[count] = "NULL";
j = j + 1;
}
i = i + 1;
count++;
}
document.write(priceDate);

Develop Reference

JavaScript is the programming language of the Web.

JS failing to populate arrays from array - javascript

You need to get values of fields from array elements. Check this: var dateArray = []; var gradeArray = []; var counter = 0; for (var member in results) { dateArray.push(member.examDate); gradeArray.push(member.grade); }

Related

Is there a way to iterate over an Object based upon the length of an array?

Making subarrays from an array algorithm javascript [duplicate]

Javascript map function to create multiple objects

array object manipulation to create new object

Comparing an Array with an Objects' Array in JavaScript

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