Develop Reference

Trouble adding 2d array contents on an HTML table

I'm making a battleship game implementation with HTML/JavaScript. This function is supposed to add the positions of the ships on an HTML table by copying the elements from a 2d array(p1Board) with the positions of the ships.
let displayTable = () => {
document.getElementById("player1turn").hidden = true;
let table = document.getElementById("player1board");
for(var i = 1; i < table.rows.length; i++){
for(var j = 1; j < table.rows.cells; j++){
table.rows[i].cells[j].innerHTML = p1Board[i - 1][j - 1];
}
}
document.getElementById("player1table").hidden = false;
}
document.getElementById("p1start").addEventListener("click", displayTable);
Then, when I open the program on my browser, the table appears but without the positions of the ships:
[Battleship Board][1]
[1]: https://i.stack.imgur.com/Nv1kA.png

The problem is that you are not specifying the row from which you want to get the cells. Also, once you get the cells, you need to access their .length property.
Change this line
for(var j = 1; j < table.rows.cells; j++)
for this
for(var j = 1; j < table.rows[i].cells.length; j++)

How do i split up an array that holds an array?

Hello my fellow JS friends,
I am letting a user import a csv file (excel sheet) and i convert that into
an array. which has 472 rows and 87 columns in this case.
so my array looks like this:
and everything is separated by commas like a usual array.
The issue is I need to separate the array within the array and when i do that i get an array with the length of 9 million, which i think is wrong
vm.allTextLines = files.split(/\r\n|\n/);
var headers = vm.allTextLines[0].split(',');
vm.columnCount = headers.length;
vm.rowCount = vm.allTextLines.length - 1;
for (var i = 0; i < vm.allTextLines.length; i++) {
// split content based on comma
var data = vm.allTextLines[i].split(',');
if (data.length == headers.length) {
var tarr = [];
for (var j = 0; j < headers.length; j++) {
tarr.push(data[j]);
}
vm.lines.push(tarr);
}
}
//this is where i split the array that contains the csv
//data and put it into its own array I believe this is
//where the issue is.
for(var i=1;i<vm.allTextLines.length; i++){
vm.uniqueAll.push(vm.allTextLines[i].split(','));
for(var j=0; j < vm.uniqueAll.length; j++){
for(var r =0; r < vm.uniqueAll[j].length; r++){
vm.arrayOfValuesOfFile.push(vm.uniqueAll[j][r]);
}
}
}
If you can help me correct this for each I would appreciate it alot.
Thank you in advance guys!

I agree with you about the place of error, because it seems you nested the loop in a wrong way. Following a snippet where you can check what I mean.
i.e:
let vm = {
allTextLines:['h1,h2,h3','row1val1,row1val2,row1val3', 'row2val1,row2val2,row2val3'],
uniqueAll: [],
arrayOfValuesOfFile:[]
}
// Here you should not nest the loop
for(var i=1;i<vm.allTextLines.length; i++){
vm.uniqueAll.push(vm.allTextLines[i].split(','));
}
for(var j=0; j < vm.uniqueAll.length; j++){
for(var r =0; r < vm.uniqueAll[j].length; r++){
vm.arrayOfValuesOfFile.push(vm.uniqueAll[j][r]);
}
}
console.log('allTextLines', vm.allTextLines);
console.log('uniqueAll', vm.uniqueAll);
console.log('arrayOfValuesOfFile', vm.arrayOfValuesOfFile);
Of Course you could easily optimize the algorithm:
let vm = {
allTextLines:['h1,h2,h3','row1val1,row1val2,row1val3', 'row2val1,row2val2,row2val3'],
uniqueAll: [],
arrayOfValuesOfFile:[]
}
for(var i=1;i<vm.allTextLines.length; i++){
let currentLinesValue = vm.allTextLines[i].split(',');
vm.uniqueAll.push(currentLinesValue);
for(var r =0; r < currentLinesValue.length; r++){
vm.arrayOfValuesOfFile.push(currentLinesValue[r]);
}
}
console.log('allTextLines', vm.allTextLines);
console.log('uniqueAll', vm.uniqueAll);
console.log('arrayOfValuesOfFile', vm.arrayOfValuesOfFile);

First you should transform you bidimensional array into a one-dimension array.
var allTogether = []; // Array with all your CSV (no matter from which file it came from)
for (var i = 0; vm.allTextLines.length; i++) {
allTogether.push(vm.allTextLines[i]); // Gets the CSV line an adds to a one-dimension array
}
// Now you can iterate over the one-dimension array
for (var i = 0; allTogether.length; i++) {
var csvFields = allTogether[i].split(',');
// Here goes your code that works with the CSV fields.
}

Referencing Javascript array element via loop variable

I've come across writing a piece of code where I wanted to reference the 2D array d2_arr[][] in a loop like so.
for (var i=0; i<d2_arr[i].length; i++) {
//do something
}
Google Script compiler throws an error "cannot read length property from undefined". When I changed [i] for [1], it worked just fine. Could anyone please explain why this is wrong? And a related question: Can a 2D array have a different number of elements in a row? theoretically. An example would be:
[[1,2],[3,4,5],[6,7,8,9],[10,11]]
EDIT. Full code part.
var ids = [];
var j = 0;
for (var i=0; i<d2_arr[i].length; i++){
if (d2_arr[i][2]<=0.05){
ids[j]=d2_arr[i][0];
j++;
}
}
I understood the mistake. Thank you!

You typically need a nested for loop to traverse a 2-D array
var d2_arr = [[1,2],[3,4,5],[6,7,8,9],[10,11]]
for (var i=0; i<d2_arr.length; i++){
for (var j=0; j<d2_arr[i].length; j++){
console.log(d2_arr[i][j] + ' ')
}
}
It is perfectly fine for arrays to be "jagged" and contain uneven sized arrays in the main array.
Here is a fiddle http://jsfiddle.net/7Lr4542s/

Arrays in JS can be of any size and any type. You can combine number and strings in array.
var twoDArray = [[1], ["one", "two"], ["i", "ii", "iii"]];
for(var i = 0; i < twoDArray.length; i++) {
for(var j = 0; j < twoDArray[i].length; j++) {
print(twoDArray[i][j]);
}
}
var threeDArray = [[["1.1.1", "1.1.2"], ["1.2.1", "1.2.2"]], [["1.2.1", "1.2.2"], ["1.2.1", "1.2.2"]], [["2.1.1", "2.1.2"], ["2.2.1", "2.2.2"]], [["2.2.1", "2.2.2"], ["2.2.1", "2.2.2"]]];
for(var i = 0; i < threeDArray.length; i++) {
for(var j = 0; j < threeDArray[i].length; j++) {
for(var k = 0; k < threeDArray[i][j].length; k++) {
print(twoDArray[i][j][k]);
}
}
}

How to add array of arrays in javascript

I have a Javascript array with multiple arrays inside. I was trying to loop through the array to return an aggregated array. So far I have done following with no luck:
var a = [[1,2,3],[4,5,56],[2,5,7]];
var x = [];
for ( var i = 0; i < a.length; i++) {
for ( var j = 0; j < a[i].length; j++) {
console.log(a[i][i] = a[i][j]+a[j][i]);
}
}
I am trying to obtain the following result:
console.log(a); // -> [7,12,66]
Any suggestions or pin points where I can look for examples of similar things would be appreciated.

assuming the elements of a has the same length, the following should work
var x=[];
for(var i=0; i<a[0].length; i++){
var s = 0;
for(var j=0; j<a.length; j++){
s += a[j][i];
}
x.push(s);
}

a[0].map(function(b,i){return a.reduce(function(c,d){return c+d[i];},0);})
// [7, 12, 66]

From dc2 to dc1, try this:
var a = [[1,2,3],[4,5,56],[2,5,7]];
var x = [];
for ( var i =0; i < a.length; i++){
for ( var j = 0; j < a[i].length; j++){
x[j] = x[j] || 0;
x[j] = x[j] + a[i][j];
}
}
This worked in testing, and doesn't error with different array lengths.

having problems with for loop in javascript

I have a table with numbers but they are stored as string so I am trying to use the function parseFloat to convert it into a table of ints. However, no matter how I do the for loops it gives me a blank table. I can parse the row and it will give me a single int. I can parse a single int as well but cant seem to parse a row or the table. here is what I have so far. This is just trying to convert one row. I tried two for loops for the entire table but that didn't work either. thanks.
var c =[];
var entries = $.parseJSON('<?php print(json_encode($try, true)); ?>');
for (var j = 0; j < 12; j++)
{
for (var i = 0; i < 7; i++)
{
c [j][i] = parseFloat(entries[j][i]);
}
}
alert(c);
here is entries json encodes [["-248","-163","-455","-1413","-1294","-1296","-1089"],["-172","-219","-1186","-1368","-1480","-1079","-845"],["-98","-198","-703","-996","-1100","-585","-616"],["-116","-241","-498","-642","-704","-354","-430"],["-137","-117","-264","-525","-533","-269","-476"],["-12","87","-257","-463","-551","-302","-535"],["170","61","-250","-472","-659","-220","-605"],["159","96","-234","-513","-617","-196","-710"],["185","117","-272","-521","-610","-258","-798"],["208","95","-234","-534","-696","-280","-854"],["192","151","-188","-641","-739","-279","-957"],["249","223","-235","-684","-763","-339","-978"]]

You have to initialize the second dimension of your array to also be an array. As it stands now, c[j] is just a single value so you can't do c[j][i] on it. There is also an error in your first for loop where you need to compare the value of j, not i. See this fixed code:
var c = [];
var entries = $.parseJSON('<?php print(json_encode($try, true)); ?>');
for (var j = 0; j < 12; j++)
{
c[j] = [];
for (var i = 0; i < 7; i++)
{
c [j][i] = parseFloat(entries[j][i]);
}
}
alert(c);

In your first loop for (var j = 0; i < 12; j++), you are using i for iteration but it is undefined and it should be j instead of i
var c =[];
var entries = $.parseJSON('<?php print(json_encode($try, true)); ?>');
for (var j = 0; j < entries.length ; j++)
{
c[j] = [];
for (var i = 0; i < entries[i].length ; i++)
{
c [j][i] = parseFloat(entries[j][i]);
}
}