Get an object from two nested array in Javascript - javascript

I want to have an object from two arrays and I did it in the following way.
for (var j = 0; j < rawDataRows.length; j++) {
for (var i = 0; i < categories.length; i++) {
var category = categories[i];
var rowValue = rawDataRows[j];
// here I do got the right value for category
console.log(category);
console.log(rowValue);
// but the following line doesn't interpret category as a variable
formattedDataRows.push({category: rowValue});
}
}
I was assuming I can get something like :
[{"category1": "value1"},{"category2": "value2"}, {"category3": "value3"}]
However, it turned out I got:
[{"category": "value1"}, {"category": "value2"}, {"category": "value3"}]
Can anyone point me where I am wrong? Also, if you have a better way achieving the goal, leave a comment please. Javascript only no jQuery or other framework. Thanks!

Object literal syntax In ECMAScript 5 and lower doesn't allow you to specify a variable identifier as property name. Instead create the object first and then use bracket notation.
var o = {};
o[category] = rowValue;
formattedDataRows.push(o);
With ECMAScript 6, you can do this:
formattedDataRows.push({[category]: rowValue});
though of course support for that syntax is limited at this point in time.

If you want both values to increment together (as it seems), also assuming the length of categories is the same length as rawdataRows, I think you really want a single loop instead of two loops:
for (var i = 0; i < categories.length; i++) {
var category = categories[i];
var rowValue = rawDataRows[i];

You can use categories[i].toString(); to get strings as you wished:
var categories = ["category1", "category2", "category3"];
var rawDataRows = ["value1", "value2", "value3"];
var formattedDataRows = [];
for (var j = 0; j < rawDataRows.length; j++) {
for (var i = 0; i < categories.length; i++) {
var category = categories[i].toString();
var rowValue = rawDataRows[j].toString();
var tmpObj = {}
tmpObj[category] = rowValue
formattedDataRows.push(tmpObj);
//formattedDataRows.push({[category]: rowValue});
}
}
document.write(JSON.stringify(formattedDataRows))

Related

Javascript array with index and multiple items on it

I've to do a strange thing and I don't know if is possible.
Let assume I've one aray
MasterArray = [1,2,3,4];
Now for each MasterArray item I need to have multiple insertion, for example under the item 1 I've to push N value, for example the MasterArray[0] must have this correlations
5,8,3,9 ...
This for any items on MasterArray.
My first idea is to create a new array one for each MasterArray items, something like this
var newobject = X;
for (i = 0; i < MasterArray.length; i++) {
Arr[i] = push the newobject ;
}
But I don't think that is a good way!
The purpose it to have a kind of correlated array.
MasterArray[0] is correlated to another array [5,8,3,9, ...]
MasterArray[1] is correlated to another array [5,6,7,1, ...]
MasterArray[2] is correlated to another array [7,45,23,2, ...]
And so on
I hope to have explained myself
Just create a 2D array in this way:
var myArray = new Array(5); // For example 5;
for (var i = 0; i < myArray.length; i++) {
myArray[i] = new Array(10);
}
Or, if you don't need to specify any size:
var myArray = new Array(5); // For example 5;
for (var i = 0; i < myArray.length; i++) {
myArray[i] = [];
}
EDIT:
For manipulate you just need to use innested loops:
for (var i = 0; i < myArray.length; i++) {
for (var j = 0; i < myArray[i].length; j++) {
myArray[i][j] = x; // where x is some variable
}
For add elements in the back just use .push() method:
myArray[0].push(5);

Google App Script arrays

I'm working on Google Script and I'm testing different ways to create two dimensions arrays.
I have created an array like this:
var codes = new Array(6);
for (var i = 0; i < 6; i++) {
codes[i] = new Array(4);
}
codes[0][0]="x";
codes[0][1]="x";
codes[0][2]="x";
codes[0][3]="x";
codes[1][0]="x";
codes[1][1]="x";
codes[1][2]="x";
codes[1][3]="x";
codes[2][0]="x";
codes[2][1]="x";
codes[2][2]="x";
codes[2][3]="x";
codes[3][0]="x";
codes[3][1]="x";
codes[3][2]="x";
codes[3][3]="x";
codes[4][0]="x";
codes[4][1]="x";
codes[4][2]="x";
codes[4][3]="x";
codes[5][0]="x";
codes[5][1]="x";
codes[5][2]="x";
codes[5][3]="x";
And it is working fine.
I read following links here, here and here.
But when I do it like this:
var codes = new Array(6);
for (var i = 0; i < 6; i++) {
codes[i] = new Array(4);
}
codes[0]=["x","x","x","x"];
codes[1]=["x","x","x","x"];
codes[2]=["x","x","x","x"];
codes[3]=["x","x","x","x"];
codes[4]=["x","x","x","x"];
codes[5]=["x","x","x","x"];
It didn't work, so I tried like this:
var codes = new Array([["x","x","x","x"],["x","x","x","x"],["x","x","x","x"],["x","x","x","x"],["x","x","x","x"],["x","x","x","x"]]);
it didn't work either.
When the code don't work, I get no error, just no display of the values.
What am I doing wrong? It looks to be the same code and the two not working ways are recommended in many documentations.
W3schools says that there is no need to use new Array().
For simplicity, readability and execution speed, use literal method ex:
var animals = ["cat", "rabbit"];
Reason why your code was not working is that you're equaling codes inside the loop and after end of loop scope 'codes' is getting only the last set array. Instead you should push those arrays to codes.
var codes = [];
for (var i = 0; i < 6; i++) {
codes.push([i]);
}
console.log(codes)
codes[0]=["x","x","x","x"];
codes[1]=["x","x","x","x"];
codes[2]=["x","x","x","x"];
codes[3]=["x","x","x","x"];
codes[4]=["x","x","x","x"];
codes[5]=["x","x","x","x"];
Better yet, two for loops to create the double array:
var codes = [], // Initiate as array, in Javascript this is actually fastre than using new (I don't know any cases you should use new)
rows = 6,
columns = 6;
for (var i = 0; i < rows; i++){
codes.push([]); // Initiate
for (var j = 0; j < columns; j++){
codes[i][j] = 'x';
}
}
Other idea, pre-initiate an array with the correct columns then copy:
var arrTemp = [],
codes = [],
rows = 6,
columns = 6;
for (var j = 0; j < columns; j++)
arrTemp[i] = 'x';
for (var i = 0; i < rows; i++)
codes.push( arrTemp.slice(0) ); // If you just push the array without slice it will make a reference to it, not copy
Other way to pre-initiate the array with 'x's:
arrTemp = Array.apply(null, Array(columns)).map(function () {return 'x'});

Javascript arrays storing values

There might be a very simple solution my problem but just not being able to find one so please help me to get to my solution in the simplest way...
The issue here is that I have data being displayed in a tabular form. Each row has 5 columns and in one of the columns it shows multiple values and so that's why I need to refer to a value by something like this row[1]['value1'], row[1]['value2'] & then row[2]['value1'], row[2]['value2'].
I declare the array
var parray = [[],[]];
I want to store the values in a loop something like this
for(counter = 0; counter < 10; counter ++){
parray[counter]['id'] += 1;
parray[counter]['isavailable'] += 0;
}
Later I want to loop through this and get the results:
for (var idx = 0; idx < parray.length; idx++) {
var pt = {};
pt.id = parray[schctr][idx].id;
pt.isavailable = parray[schctr][idx].isavailable;
}
Obviously iit's not working because Counter is a numeric key and 'id' is a string key ..my question how do I achieve this ??
Thanks for all the answers in advance.
JS has no concept of "associative arrays". You have arrays and objects (map). Arrays are objects though, and you can put keys, but it's not advisable.
You can start off with a blank array
var parray = [];
And "push" objects into it
for(counter = 0; counter < 10; counter++){
parray.push({
id : 1,
isAvailable : 0
});
}
Then you can read from them
for (var idx = 0; idx < parray.length; idx++) {
// Store the current item in a variable
var pt = parray[idx];
console.log(pt);
// read just the id
console.log(parray[idx].id);
}
Like I did here
What you want inside your array is just a plain object:
// just a regular array
var parray = [];
for(var counter = 0; counter < 10; counter++){
// create an object to store the values
var obj = {};
obj.id = counter;
obj.isavailable = 0;
// add the object to the array
parray.push(obj);
}
later:
for (var idx = 0; idx < parray.length; idx++) {
var pt = parray[idx];
// do something with pt
}

Pushing value into a multidimensional array

I have surfed the problem but couldn't get any possible solution ..
Let's say i have a var like this
var data = [
{
'a':10,
'b':20,
'c':30
},
{
'a':1,
'b':2,
'c':3
},
{
'a':100,
'b':200,
'c':300
}];
Now , i need a multidimensional array like
var values = [[10,1,100], //a
[20,2,200], //b
[30,3,300]]; //c
What i have tried is
var values = [];
for(var key in data[0])
{
values.push([]); // this creates a multidimesional array for each key
for(var i=0;i<data.length;i++)
{
// how to push data[i][key] in the multi dimensional array
}
}
Note : data.length and number of keys keeps changing and i just want to be done using push() without any extra variables. Even i don't want to use extra for loops
If you guys found any duplicate here , just put the link as comment without downvote
Try this:
var result = new Array();
for(var i = 0; i < data.length; i++) {
var arr = new Array();
for(var key in data[i]) {
arr.push(data[i][key]);
}
result.push(arr);
}
also if you don't want the 'arr' variable just write directly to the result, but in my opinion code above is much more understandable:
for(var i = 0; i < data.length; i++) {
result.push(new Array());
for(var key in data[i]) {
result[i].push(data[i][key]);
}
}
Ok, based on your comment I have modified the the loop. Please check the solution and mark question as answered if it is what you need. Personally I don't understand why you prefer messy and hard to understand code instead of using additional variables, but that's totally different topic.
for(var i = 0; i < data.length; i++) {
for(var j = 0; j < Object.keys(data[0]).length; j++) {
result[j] = result[j] || new Array();
console.log('result[' + j + '][' + i + ']' + ' = ' + data[i][Object.keys(data[i])[j]])
result[j][i] = data[i][Object.keys(data[i])[j]];
}
}

How to loop through Nested Json Array with (JavaScript) for loop and display the text

This may be a fairly simple question but it's just not working for me no matter how many times I change the for loop around. So how would you loop through this array using a for loop in JavaScript?
var fielditems =[
[["News Tips"],["Opinions"],["MedMinutes"]],
[["Yes"],["No"],["Maybe"]],
[["How"],["Why"],["When"]]
];
This is what I have and it's not working. I used an alert to just test out the result but it's not even returning anything.
for(itemSet in fielditems){
var itemSetValues = fielditems[itemSet];
for(set in itemSetValues){
var itemValue = itemSetValues[set];
for(value in itemvalue){
alert(itemValue[value]);
}
}
}
What am I doing wrong?
Don't use for() with in for arrays. It's for object properties. Use the standard format instead.
Demo: http://jsfiddle.net/ThinkingStiff/EVWch/
Script:
var fielditems =[
[["News Tips"],["Opinions"],["MedMinutes"]],
[["Yes"],["No"],["Maybe"]],
[["How"],["Why"],["When"]]
];
for( var itemIndex = 0; itemIndex < fielditems.length; itemIndex++ ){
var itemSetValues = fielditems[itemIndex];
for(var setIndex = 0; setIndex < itemSetValues.length; setIndex++ ){
var itemValue = itemSetValues[setIndex];
for(var valueIndex = 0; valueIndex < itemValue.length; valueIndex++ ){
alert(itemValue[valueIndex]);
};
};
};
​
Firstly, console is your friend. You get error ReferenceError: itemvalue is not defined because javascript is case sensitive. Change itemvalue in the most nested loop to itemValue.
Secondly, if you want iterate thorugh an array, you should use for-loop instead for-in-loop
Don't use for-in loops on arrays
Don't use (running) variables without declaring them as local
for (var i=0; i<fielditems.length; i++) {
var itemSetValues = fielditems[i];
for (var j=0; j<itemSetValues.length; j++) {
var itemvalue = itemSetValues[j]; // notice the case
for (var k=0; k<itemvalue.length; k++) {
alert(itemvalue[k]);
}
}
}
for..in is for objects ({}), not for arrays ([]).
You need to use a standard for loop.
for(var i = 0, iLen = fielditems.length; i < iLen; i++){
var iItem = fielditems[i];
for(var j = 0, jLen = iItem.length; j < jLen; j++){
var jItem = iItem[j];
alert(jItem[0]); // you can also add another loop here, if this will have more elements
}
}
NOTE:
for(var i = 0, iLen = fielditems.length; i < iLen; i++)
is better than:
for(var i = 0; i < fielditems.length; i++)
because fielditems.length isn't requested each loop, just once at the start.

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