Develop Reference

ID to many elements elements

I have maybe weird question, but it is very important to me to solve this.
I have table wich is not with stable amount of rows and columns, so i put the += operator to create cells, rows and etc. Now i need to identify every cell, but i don't understand how i can do it in this situation.
function drawBoard(board) {
var t="";
t="<table border: 2px >";
var x,y;
for(x=0; x<board.length; x++){
t+="<tr>";
for(y=0; y<board.length; y++){
t+="<td class='tablecell' onclick=''>X</td>"
}
t+="</tr>";
}
t+="</table>";
}

By identify a cell I'm assuming you would like to reference them later in different part of the code.
You could achieve it by giving your rows and cells classes and/or ids.
For a row, for example:
t += '<tr id="tr-' + x + '">';
for a cell
t += '<td class="tablecell tr-' + x + ' col-' + y + '" onclick="" id="td-' + x + '-' + y + '">X</td>'
Then rows can be referenced by #tr-x and cells #tr-x > td, and all specific columnd .col-y
As Matheus Avellar mentioned, added id to a cell as well in case you want to reference a particular cell on a grid using #td-x-y

You are able to use:
const cells = document.getElementsByClassName('tablecell')
Or you can collect every cell on the stage of creation, for example:
const cells = [];
for (let i = 0; i < board.length){
for (let j = 0; j < board.length){
const cell = document.createElement('td');
cells.push(cell);
}
}

You can set the id of each one equal to your 'y' variable.
Something like:
function drawBoard(board) {
var t = "";
t = "<table border: 2px >";
var x, y;
for (x = 0; x < board.length; x++) {
t += "<tr>";
for (y = 0; y < board.length; y++) {
t += `<td id="table-${y}" class='tablecell' onclick=''>X</td>`
}
t += "</tr>";
}
t += "</table>";
}
Using a bit of ES6 template literals, you can set tie your ID to your 'Y' variable since it's an incrementing number.

Printing a formatted multiplication table to the console

my current code currently prints a table to the console, but I want the table to be formatted so every column and row are aligned perfectly. I can do that using an HTML table, but I would prefer just printing in the console.
console.log(multiplicationTable(12));
function multiplicationTable(max)
{
var i,j;
for( i = 1; i<=max ; i++)
{
for( j = 1; j<=max; j++)
{
document.write( i*j + " " );
}
document.write("<br>");
}
}
Thanks a lot!

How about using the "console.table(~~)" ?

The trick is to use another string contain spaces to join your string.
You can have a look at this: Here
Short answer:
var str = ""; //your string
var pad = "0000"; //the buffer string
var ans = pad.substring(0, pad.length - str.length) + str //get the length of your buffer and minus your string to get the remaining '0'.

Here is a formatted table inside your console:
console.log(multiplicationTable(12));
function multiplicationTable(max) {
var i, j;
document.write("<table border='1'>");
for (i = 1; i <= max; i++) {
document.write("<tr>");
for (j = 1; j <= max; j++) {
document.write("<td>" + i * j + "</td>");
}
document.write("</tr>");
}
document.write("</table>");
}

Trying to pass by value in Javascript multi-dim array

So, I'm building a web site that you can play othello on as a code sample. I've got a multidimensional array as the behind-the-scenes gameboard, and then iterate through every 'td' in a table to match the value of the corresponding array member. The problem i'm encountering is that iterating through the table. and using the iterators as essentially coordinates to my array doesn't work. As the iterator increases in value, so too does the coordinates in each of my 'td's. I'm stumped, and running on fumes. Any help would be appreciated.
function gridArray() {
// creates game board's array.
for (var i = 0; i < gameArray.length; i++) {
gameArray[i] = new Array(8);
}
for (var row = 0; row < gameArray.length; row++) {
for (var col = 0; col < gameArray[row].length; col++) {
gameArray[row][col] = "green";
}
}
}
function drawGrid(){
// writes table to HTML document
var htmlString = "<table id='othelloGrid'><tr>";
for (var i = 0; i < 8; i++) {
htmlString += "<th>" + i + "</th>";
}
htmlString += "</tr>";
for (var j = 0; j < 8; j++) {
htmlString += "<tr>";
xPos = j;
for (var x = 0; x < 8; x++) {
yPos = x;
// HERE!!! I now realize javascript passes by reference, so as this loop iterates,
// every single 'td' is getting 'onclick = 'changeClass(7, 7)''.
// for my game grid to work, I need each td to have a unique xPos, yPos to
// connect back to gameArray.
htmlString += "<td onclick = 'changeClass(xPos, yPos)'></td>";
}
htmlString += "</tr>";
}
htmlString += "</table>";
return htmlString;
}

Variables are not expanded inside strings. So all your TDs have the literal attribute onclick='changeClass(xPos, yPos)' in them, not the values of these variables from the loop. So when you actually click on them, they all use the most recent values of those variables.
You need to use string concatenation to get the values. And there's no need for the global variables xPos and yPos, you can use the local j and x variables.
htmlString += "<td onclick = 'changeClass(" + j + ", " + x + ")'></td>";

How to calculate how many rows and columns are needed

I want to produce a table with Javascript. I want to give it a number and that's how many cells are created. There are always to be 3 columns however (3 pictures per row)
Could someone help me out with this? I think I need to use the modulus operator but I am unsure of how to use it correctly.
I do not want any extra cells. I can calculate the rows without issue but I don't want extra cells for those rows if that makes sense. So once the cells have been made that row ends even if it's 1 or 2 cells short.
I have this at the moment:
rows = ?? //Not sure how to calculate this
columns = 3;
str = "";
str += '<table border="1" cellspacing="1" cellpadding="5">';
for(i = 0; i < rows; i++){
str += '<tr>';
for (j = 0; j < columns; j++){
str += '<td>' + (i + j) + '</td>';
}
str += '</tr>';
}
str += '</table>';

Say if u have number of pictures as numPictures:-
Then
var numRows = Math.ceil(numPictures/3);

I hope the following code that what you want.
var numOfPics = 100; // Number of Pictures
var columns = 3, rows = Math.ceil(numOfPics / columns), content = "", count = 1;
content = "<table border='1' cellspacing='1' cellpadding='5'>";
for (r = 0; r < rows; r++) {
content += "<tr>";
for (c = 0; c < columns; c++) {
content += "<td>" + count + "</td>";
if (count == numOfPics)break; // here is check if number of cells equal Number of Pictures to stop
count++;
}
content += "</tr>";
}
content += "</table>";
document.body.innerHTML = content; // insert `content` value into body of page

You know how many cells there are. So you divide the number of cells by the number of columns to get the number of rows. Math.ceil() rounds up in case there are not the exact amount of cells to fill a row.
rows = Math.ceil(total_num_cells / 3);

Need help w/ JavaScript and creating an html table from array

I've tried everything I can find via google and nothing has worked correctly. Output is just a single row with all the contents of the array listed. What I need is a way to write the contents of an array but after 3 cells, automatically start a new line. I'll post the code I've made below as well as the question. (yes this is from an assignment. :( )
//***(8) place the words in the string "tx_val" in a table with a one pixel border,
//*** with a gray backgound. Use only three cells per row. Empty cells should contain
//*** the word "null". Show the table in the span block with id="ans8"
var count = i % 3;
var nrow = "";
var out = "<table border='1' bgcolor='gray'><tr>"
for (var i=0; i<txArr.length; i++)
{
out += ("<td>" + txArr[i] + "</td>");
count++;
if (count % 3 == 0)
{
nrow += "</tr><tr>";
}
}
document.getElementById('ans8').innerHTML = out + nrow;

you need to print the tr's inside the table (annd add a </table>!):
var count = i % 3; // btw. what's this??
var nrow = "";
var out = "<table border='1' bgcolor='gray'><tr>"
for (var i=0; i<txArr.length; i++)
{
out += "<td>" + txArr[i] + "</td>";
count++;
if (count % 3 == 0)
out += "</tr><tr>";
}
out += "</table>";
document.getElementById('ans8').innerHTML = out;

Rather than try to write out the html, try manipulating the dom. It seems much more straightforward to me. Take a look at the following:
var row = table.insertRow();
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var cell = row.insertCell();
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var cellContent = document.createTextNode(txArr[i]);
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cell.appendChild(cellContent);
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For deciding when to start a new row, just use the modulus operator (%
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) against i:
if (i % 3 == 0)
{
row = table.insertRow()
}
You'd end up with something like this:
var container = document.getElementById("ans8");
var t = container.appendChild(document.createElement("table"));
var row;
txArr.forEach(function (item, i)
{
if (i % 3 == 0)
{
row = t.insertRow()
}
row.insertCell().appendChild(document.createTextNode(item));
});
I'll leave a little for you to figure out - border, background color, getting the word "null" in there. It is your homework after all. :-)
Also, for older browsers you'll need to add Array.forEach in yourself.

I prefer using an array over concatination
var html = [];
html.push("<table><tr>");
var i = 0;
for (var k in txArr)
{
if(i>=3){
i=0;
html.push("</tr><tr>");
}
html.push("<td>" + txArr[k] + "</td>");
i++;
}
html.push("</tr></table>");
document.getElementById('ans8').innerHTML = html.join('');
// wrapped in function
function arrayToTable(a,cols){
var html = [];
html.push("<table><tr>");
var i = 0;
for (var k in a)
{
if(i>=cols){
i=0;
html.push("</tr><tr>");
}
html.push("<td>" + a[k] + "</td>");
i++;
}
html.push("</tr></table>");
return html.join('')
}
document.getElementById('ans8').innerHTML = arrayToTable(txArr, 3);

It might be a tad easier to accomplish with something like
buffer = "<table>";
for(var r = 0; r < 10; r++){
buffer += "<tr>";
for(var c = 0; c < 3 ; c++){
buffer += "<td>Cell: " + r + ":" + c + "</td>";
}
buffer += "</tr>";
}
buffer += "</table>";
document.getElementById("ans8").innerHTML = buffer;
That would create a table 30 rows long by 3 columns for each row.

you might be assigning values to "count" too early as you don't know what i is yet. and you are not spitting out the value of nrow anywhere... change it to out.
var count;
var nrow = "";
var out = "<table border='1' bgcolor='gray'><tr>"
for (var i=0; i<txArr.length; i++)
{
out += ("<td>" + txArr[i] + "</td>");
count++;
if (count % 3 == 0)
{
out += "</tr><tr>";
}
}
document.getElementById('ans8').innerHTML = out + nrow;

Basically I would split it up into 3 functions, for readability and maintenance. These functions would consist of creating a cell, a row, and a table. This definitely simplifies reading the code. As I have not tested it, below is an example of what I would do.
function createTableCell(value) {
return value == null? "<td>NULL</td>":"<td>" + value + "</td>";
}
function createTableRow(array) {
var returnValue = "";
for (var i = 0; i < array.length; i++) {
returnValue = returnValue + createTableCell(array[i]);
}
return "<tr>" + returnValue + "</tr>";
}
function arrayToTable(array, newRowAfterNArrayElements) {
var returnValue = "<table>";
for (var i = 0; i < array.length; i = i + newRowAfterNArrayElements) {
returnValue = returnValue + createTableRow(array.split(i, (i + newRowAfterNArrayElements) - 1));
}
return returnValue + "</table>";
}
document.getElementById("ans8").innerHTML = arrayToTable(txArr, 3);
In addition this makes your code much more dynamic and reusable. Suppose you have an array you want to split at every 4 element. Instead of hardcoding that you can simply pass a different argument.

Here's a live example of doing this with DOMBuilder, and of using the same code to generate DOM Elements and an HTML String.
http://jsfiddle.net/insin/hntxW/
Code:
var dom = DOMBuilder.elementFunctions;
function arrayToTable(a, cols) {
var rows = [];
for (var i = 0, l = a.length; i < l; i += cols) {
rows.push(a.slice(i, i + cols));
}
return dom.TABLE({border: 1, bgcolor: 'gray'},
dom.TBODY(
dom.TR.map(rows, function(cells) {
return dom.TD.map(cells);
})
)
);
}
var data = [1, 2, null, 3, null, 4, null, 5, 6];
document.body.appendChild(arrayToTable(data, 3));
document.body.appendChild(
dom.TEXTAREA({cols: 60, rows: 6},
DOMBuilder.withMode("HTML", function() {
return ""+arrayToTable(data, 3);
})
)
);

Yes, you can build from scratch...but there's a faster way. Throw a grid at it. The grid will take data in a string, array, json output, etc and turn it into a proper HTML outputted table and will allow you to extend it with sorting, paging, filtering, etc.
My personal favorite is DataTables, but there are numerous others out there.
Once you get proficient, setting one of these up literally takes 5 minutes. Save your brain power to cure world hunger, code the next facebook, etc....