Treat the prev element in JavaScript array when creating object dynamically - javascript

I want to do something like:
var arr = []
for var(i=0;i<x;i++){
arr.push{ get num(){return this.previousArrayElement.num + randomNumber}}
}
how can I treat "previousArrayElement"?

I think you are just trying to create an array of size x containing numbers in order of size and separated by randomNumber intervals? Something like this would work:
var x = 100;
var arr = [0]
for (i=1; i<x; i++) {
arr.push( arr[i-1] + Math.random() );
}
Note that by starting the array out with an initial value (index 0) and beginning your iteration with the second value (index 1) you don't have to worry about accessing the 0-1 element at the first iteration.
I hope that helps!

Not 100% sure this is what you want. Expected output shown is not valid syntax and details provided are very open to interpretation
var arr = []
for (var i=0; i < x; i++){
var num = i > 0 ? arr[i-1].num : 0;
num= num + randomNumber; // is this an existing variable?
arr.push({ num: num}); // used object with property `num` based on example `previousArrayElement.num `
}

Related

Pass array values to another array

I have an array of input fields called '$inputFieldsArray' then I slice them to group by 3 into 'newArray' then I need new array value for each item to assign to another array cause in the end I need an array with input fields values grouped by 3. The end goal is to get an array which contains for 9 input fields ex [[i1,i2,i3],[i4,i5,i6],[i7,i8,i9]].
For some reason 'stringArray' output is nothing, first two arrays print correct results. It's probably some mistake I do regarding JS arrays.. Sorry js is not my main language, I try to learn it. Thanks.
Here is a screenshoot with chrome console:
Here is my function:
$($submitButton).click(function () {
// Get number of input fields
let $total = $("input[name^='bodyHeader']").length;
// Get input fields as objects
let $inputFieldsArray = $("input[name^='bodyHeader']");
let newArray = [];
let stringArray = [];
let j = 0;
// Group input fields by 3
for (let i = 0; i < $total - 1; i += 3) {
newArray[j] = $inputFieldsArray.slice(i, i + 3);
j++;
}
// Extract string values from newArray and pass them into stringArray
for (let k = 0; k < newArray.length - 1; k++) {
stringArray[k][0] = newArray[k][0].value;
stringArray[k][1] = newArray[k][1].value;
stringArray[k][2] = newArray[k][2].value;
}
// Print to test results
console.log($inputFieldsArray);
console.log(newArray);
console.log("String Array: " + stringArray);
... // Function logic is not complete
});
SOLUTION:
There is no way to declare dynamic length bidimensional array in js. Use this approach suggested by #Stephan :
stringArray[k] = [newArray[k][0].value, newArray[k][1].value,
newArray[k[2].value];
or this approach suggested by #Lorenzo Gangi:
var matrix = [],
cols = 3;
//init the grid matrix
for ( var i = 0; i < cols; i++ ) {
matrix[i] = [];
}
stringArray[k] is undefined because you defined stringArray as [] (Your browser probably threw an exception). Additionally newArray[k] starts at index 0.
You could write stringArray[k] = [newArray[k][0].value, newArray[k][1].value, newArray[k][2].value] instead.
Basically,
stringArray[k]
is undefined yet, therefore setting its [0] property wont work. May do:
stringArray[k] =newArray[k].map(el=>el.value);
Alltogether:
$($submitButton).click(function () {
let stringArray = $("input[name^='bodyHeader']").toArray().reduce((res,_,i,arr)=>((i%3==0 && res.push(arr.slice(i,i+3).map(e=>e.value))),res),[]);
});

JS loop does not works (variable undefined but single selection works)

I'm completely stumped..
I uploaded a csv file to my database and now my application should "play" with it..
After my select, I want to split this file into his elements. This is my code:
var file = result[0].FILE;
var entries;
var lines = {
line: []
};
var i;
var allLines = file.split(/[\r\n]+/g);
for(i = 0; i <= allLines.length; i++) {
entries = allLines[i].split(';');
lines.line.push({
DATEVALUE: entries[0],
VALUE: entries[1]
});
}
I'm getting this error:
allLines[i]is not defined
Well... allLines has a length of 182 elements and if I use something like allLines[0]or allLines[1] instead of allLines[I] everything is okay. But why does the loop does not works?
My select looks like (Output with JSON.stringify()):
[
"2014-01-01 00:00:00;309",
"2014-01-02 00:15:00;198",
"2014-01-03 00:30:00;274",
"2014-01-04 00:45:00;140",
"2014-01-05 01:00:00;167",
"2014-01-06 01:15:00;276",
"2014-01-07 01:30:00;283",
"2014-01-08 01:45:00;304", ... ]
Arrays are 0-indexed (their subscripts start from 0). So if an array contain N elements and the first element is 0 then the last element will be N - 1 not N. So array[array.length] is undefined. Change the for loop from this:
for(i = 0; i <= allLines.length; i++) {
// ...
to this:
for(i = 0; i < allLines.length; i++) {
// ...
MATH:
TheNumberOfItems = LastItemIndex - FirstItemIndex + 1;
so:
array.length = x - 0 + 1; // where x is the index of the last item
then:
x = array.length - 1;
so the last element of the array is array.length - 1 not array.length. So if the condition for the loop was i <= array.length then at some point array[array.length] will be evaluated (to undefined).

Accessing indexes of a string inside an array and taking the sum

Ok so I am trying to access each individual number in the strings inside of this array.
var array = ['818-625-9945','999-992-1313','888-222-2222','999-123-1245'];
var str = "";
for (i=0; i<array.length; i++) {
str = array[i];
}
The problem is that this is the output: '999-992-1313'
and not the first element array[0]: '818-625-9945'
When I try doing a nested for loop to go through each element inside the string I am having trouble stating those elements.
var array = ['818-625-9945','999-992-1313','888-222-2222','999-123-1245'];
for (i=0; i<array.length; i++) {
for (j=0; j<array[i].length; j++) {
console.log(array[i][j]);
}
}
I do not know how to access each individual number inside of the string array[i]. I would like to find a way to make a counter such that if I encounter the number '8' I add 8 to the total score, so I can take the sum of each individual string element and see which number has the highest sum.
var array = ['818-625-9945','999-992-1313','888-222-2222','999-123-1245'];
for (i=0; i<array.length; i++) {
for (j=0; j<array[i].length; j++) {
if (array[i](j).indexOf('8') !== -1) {
// add one to total score
// then find a way to increase the index to the next index (might need help here also please)
}
}
}
Mabe this works for you. It utilized Array.prototype.reduce(), Array.prototype.map() and String.prototype.split().
This proposal literates through the given array and splits every string and then filter the gotten array with a check for '8'. The returned array is taken as count and added to the return value from the former iteration of reduce - and returned.
var array = ['818-625-9945', '999-992-1313', '888-222-2222', '999-123-1245'],
score = array.reduce(function (r, a) {
return r + a.split('').filter(function (b) { return b === '8'; }).length;
}, 0);
document.write('Score: ' + score);
A suggested approach with counting all '8' on every string:
var array = ['818-625-9945', '999-992-1313', '888-222-2222', '999-123-1245'],
score = array.map(function (a) {
return a.split('').filter(function (b) { return b === '8'; }).length;
});
document.write('Score: ' + score);
Actually rereading your question gave me a better idea of what you want. You simply want to count and retrieve the number of 8's per string and which index in your array conforms with this maximum 8 value. This function retrieves the index where the value was found in the array, how many times 8 was found and what is the string value for this result. (or returns an empty object in case you give in an empty array)
This you could easily do with:
'use strict';
var array = ['818-625-9945', '999-992-1313', '888-222-2222', '999-123-1245'];
function getHighestEightCountFromArray(arr) {
var max = 0,
result = {};
if (arr && arr.forEach) {
arr.forEach(function(value, idx) {
var cnt = value.split('8').length;
if (max < cnt) {
// found more nr 8 in this section (nl: cnt - 1)
max = cnt;
// store the value that gave this max
result = {
count: cnt - 1,
value: value,
index: idx
};
}
});
}
return result;
}
console.log(getHighestEightCountFromArray(array));
The only thing here is that when an equal amount of counts is found, it will still use the first one found, here you could decide which "maximum"
should be preferred(first one in the array, or the newest / latest one in the array)
OLD
I'm not sure which sums you are missing, but you could do it in the following way.
There I first loop over all the items in the array, then I use the String.prototype.split function to split the single array items into an array which would then contain ['818', '625', '9945']. Then for each value you can repeat the same style, nl: Split the value you are receiving and then loop over all single values. Those then get convert to a number by using Number.parseInt an then all the values are counted together.
There are definitelly shorter ways, but this is a way how you could do it
'use strict';
var array = ['818-625-9945','999-992-1313','888-222-2222','999-123-1245'],
sumPerIndex = [],
totalSum = 0;
array.forEach(function(item, idx) {
var values = item.split('-'), subArray = [], itemSum = 0;
values.forEach(function(value) {
var singleItems = value.split(''),
charSum = 0;
singleItems.forEach(function(char) {
charSum += parseInt(char);
});
itemSum += charSum;
subArray.push(charSum);
console.log('Sum for chars of ' + value + ' = ' + charSum);
});
sumPerIndex.push(subArray);
totalSum += itemSum;
console.log('Sum for single values of ' + item + ' = ' + itemSum);
});
console.log('Total sum of all elements: ' + totalSum);
console.log('All invidual sums', sumPerIndex);

Using search method from string

I'm trying to count the number of times certain words appear in the strings. Every time I run it I get a
uncaught TypeErro: undefined is not a function
I just actually need to count the number of times each "major" appears.
Below is my code:
for(var i = 0; i < sortedarray.length; i++)
{
if(sortedarray.search("Multimedia") === true)
{
multimedia += 1;
}
}
console.log(multimedia);
Here is my csv file which is stored in a 1d array.
"NAME","MAJOR","CLASS STANDING","ENROLLMENT STATUS"
"Smith, John A","Computer Science","Senior","E"
"Johnson, Brenda B","Computer Science","Senior","E"
"Green, Daisy L","Information Technology","Senior","E"
"Wilson, Don A","Information Technology","Junior","W"
"Brown, Jack J","Multimedia","Senior","E"
"Schultz, Doug A","Network Administration","Junior","E"
"Webber, Justin","Business Administration","Senior","E"
"Alexander, Debbie B","Multimedia","Senior","E"
"St. John, Susan G","Information Technology","Junior","D"
"Finklestein, Harold W","Multimedia","Freshman","E"
You need to search inside each string not the array. To only search inside the "Major" column, you can start your loop at index 1 and increment by 4 :
var multimedia = 0;
for(var i = 1; i < sortedarray.length; i += 4)
{
if(sortedarray[i].indexOf("Multimedia") > -1)
{
multimedia += 1;
}
}
console.log(multimedia);
What you're probably trying to do is:
for(var i = 0; i < sortedarray.length; i++)
{
if(sortedarray[i].indexOf("Multimedia") !== -1)
{
multimedia++;
}
}
console.log(multimedia);
I use indexOf since search is a bit of overkill if you're not using regexes.
Also, I replaced the += 1 with ++. It's practically the same.
Here's a more straightforward solution. First you count all the words using reduce, then you can access them with dot notation (or bracket notation if you have a string or dynamic value):
var words = ["NAME","MAJOR","CLASS STANDING","ENROLLMENT STATUS"...]
var count = function(xs) {
return xs.reduce(function(acc, x) {
// If a word already appeared, increment count by one
// otherwise initialize count to one
acc[x] = ++acc[x] || 1
return acc
},{}) // an object to accumulate the results
}
var counted = count(words)
// dot notation
counted.Multimedia //=> 3
// bracket notation
counted['Information Technology'] //=> 3
I don't know exactly that you need this or not. But I think its better to count each word occurrences in single loop like this:
var occurencesOfWords = {};
for(var i = 0; i < sortedarray.length; i++)
{
var noOfOccurences = (occurencesOfWords[sortedarray[i]]==undefined?
1 : ++occurencesOfWords[sortedarray[i]]);
occurencesOfWords[sortedarray[i]] = noOfOccurences;
}
console.log(JSON.stringify(occurencesOfWords));
So you'll get something like this in the end:
{"Multimedia":3,"XYZ":2}
.search is undefined and isn't a function on the array.
But exists on the current string you want to check ! Just select the current string in the array with sortedarray[i].
Fix your code like that:
for(var i = 0; i < sortedarray.length; i++)
{
if(sortedarray[i].search("Multimedia") === true)
{
multimedia += 1;
}
}
console.log(multimedia);

How to split and add individual values in a string?

In my javascript, I've an array named my_array holding values like 0121, 1201, 0012, 0202 etc.
Each individual digit in the string is of importance. So, in the above example, there are 4 values in one string. E.g. 0121 holds 0,1,2,1.
The values can also be longer too. E.g. 01221, 21021 etc. (This is holding 5 values)
I want to know of the easiest and most effective way to do the following:
Add the first digits of all the strings in the array my_array. E.g. 0+1+0+0 in the above example
Add the second digits (e.g. 1+2+0+2) and so on.
I can loop through the array and split the values, then
for(i=0; i<my_array.length; i++){
var another_array = my_array[i].split();
//Getting too complicated?
}
How can I do it effectively? Someone please guide me.
Something like this
var myArray = ["0121", "1201", "0012", "0202"];
var firstValSum = 0;
for(var i = 0; i < myArray.length; i++) {
var firstVal = myArray[i].split("");
firstValSum += parseInt(firstVal[0], 10);
}
console.log(firstValSum); //1
This could be wrapped into a function which takes parameters to make it dynamic. i.e pass in the array and which part of the string you want to add together.
EDIT - This is a neater way of achieving what you want - this code outputs the computed values in an array as you specified.
var myArray = ["0121", "1201", "0012", "0202"];
var newArr = [];
for(var i = 0; i < myArray.length; i++) {
var vals = myArray[i].split("");
for(var x = 0; x < vals.length; x++) {
var thisVal = parseInt(vals[x], 10);
( newArr[x] !== undefined ) ? newArr[x] = newArr[x] += thisVal : newArr.push(thisVal);
}
}
console.log(newArr); //[1, 5, 3, 6];
Fiddle here
var resultArray = new Array(); // This array will contain the sum.
var lengthEachString = my_array[0].length;
for(j=0; j<lengthEachString ; j++){ // if each element contains 4 elements then loop for 4 times.
for(i=0; i<my_array.length; i++){ // loop through each element and add the respective position digit.
var resultArray[j] = parseInt( my_array[i].charAt(j) ); // charAt function is used to get the nth position digit.
}
}

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