Develop Reference

JavaScript eval() not working with variable name

why eval() is not executing my code?
for (var i = 1; i <= 3; i++) {
str = "var foo_" + i + "_bar = " + i;
eval(str);
}
console.log(foo_1_bar);
console.log(foo_2_bar);
console.log(foo_3_bar);

The variable foo_2_bar is not declared at that iteration (i = 1). You need to put the console.log(...) outside of the loop.
I assume you're playing with js because eval is a little dangerous.
for (var i = 1; i <= 3; i++) {
str = "var foo_" + i + "_bar = " + i;
eval(str);
}
console.log(foo_1_bar);
console.log(foo_2_bar);
console.log(foo_3_bar);

Your logged variable doesn't exist
for (var i = 1; i <= 3; i++) {
str = "var foo_"+ i +"_bar = " + i;
eval(str);
console.log(foo_1_bar);
}

How to print a half pyramid in javascript

The code works but I don't want the inner for loop to take me to the new line.
for (i = 0; i < 5; i++) {
for (j = 1; j <= i; j++) {
console.log('*');
}
console.log();
}
console.log('-----------------');

console.log will automatically break the line. Concatenate to a string instead of a log. Log at the end.
let str = '';
for(i = 0; i <= 5 ; i++) {
for(j = 1; j <= i; j++) {
str += '*';
}
str += '\n';
}
console.log(str);

You can do this way, with the help of a string variable:
for (i = 0; i < 5; i++) {
var str = '';
for (j = 1; j <= i; j++) {
str+='*';
}
console.log(str);
}
console.log('-----------------');

If you want to print at the page, use like below
for (i = 0; i < 5; i++) {
let j=0;
do{document.write("*");j++;}while(j < i)
document.write("<br/>")
}

You need to break the line with the console.log you can also controle the space between * with output+='*' + " ";
function pyramid() {
var total = 5;
var output="";
for (var i = 1; i <= total; i++) {
for (var j = 1; j <= i; j++) {
output+='*' + " ";
}
console.log(output);
output="";
}
}
pyramid()

You can get rid of second for loop as follows:
var str = '';
for (i = 1; i <= 5; i++) {
str +=Array(i).join("*");
str +='\n';
}
console.log(str);

let string = "";
for (let i = 0; i < 5; i++){
string += '*';
console.log(string);
}
Output:
*
**
***
****
*****

A simple way to solve this "exercise" in JavaScript:
let width = ""
while(width.length < 6) console.log(width += `#` );
Basically, we create a string (width) and increment its value using the while loop till we hit a restriction.
I found the more typical method "bulky"(?)...plus there's the issue of not getting the exact picture of a half pyramid.
let i,j
for (i= 0; i < 6; i++){
for (j = 0; j<=i; j++){
console.log("#")
}
console.log("\n")
}

function pyramid(n){
let result = "";
for(let i=0; i<=n; i++){
result += "*".repeat(i);
result += "\n"
}
return result;
}
console.log(pyramid(5));
//OutPut
*
**
***
****
*****
As we need n number of pyramid structure with '' / '#' / any symbol. by using above code we can achieve. Here you can see we just created a function called pyramid with one parameter 'n'. and inside function we declare a variable 'result'. So inside for loop the length of 'i' is "<=n" and also you can use "repeat() method to print '' 'i' times. So if you call that function like console.log(pyramid(5)); You can able to see your Answer as expected..

shortest code:
console.log('*\n**\n***\n****\n*****');

Building a JavaScript grid with odd and even characters using two loops

This is my first question on StackOverflow.
I have to build gridGenerator(num). If num is 3, it would look like this:
#_#
_#_
#_#
If num is 4, it would look like this:
#_#_
_#_#
#_#_
_#_#
I was able to solve it for odd numbers, but struggle to adjust it to even numbers.
function gridGenerator(num) {
var grid = '';
var row = '';
for (var i = 0; i < num; i++) {
for (var j = 0; j < num; j++) {
if (row.length % 2) {
row += '_';
} else {
row += '#';
}
}
grid += row.slice(-num) + '\n';
}
return grid;
}
console.log(gridGenerator(3));
Need a hint how to solve it for 2, 4, and other even numbers. Thank you!

Try this
if ((i+j) % 2)
function gridGenerator(num) {
var grid = '';
var row = '';
for (var i = 0; i < num; i++) {
for (var j = 0; j < num; j++) {
if ((i+j) % 2) {
row += '_';
} else {
row += '#';
}
}
grid += row.slice(-num) + '\n';
}
return grid;
}
console.log(gridGenerator(4));

You can use the condition num % 2 to determine if a number is even or odd. I would use two loops like you are doing. Make your character addition based on the even / odd state of the row and column. At the end of each row insert the line break.
EDIT: Here you go.
function generateGrid( num ) {
let i, j, grid = "";
for ( i = 0; i < num; i++ ) {
for ( j = 0; j < num; j++ ) {
if ( ( i + j ) % 2 ) {
grid += "_";
} else {
grid += "#";
}
}
grid += "\n";
}
return grid;
}
var grid = generateGrid( 4 );
console.log( grid );

function gridGen(num) {
var even = '';
for (var i = 0; i< num ; i++)
even += (i%2) ? '_' : '#';
odd = even.substring(1) + (num%2 ? '_' : '#');
var out = '';
for (var i = 0; i< num ; i++)
out += ((i%2) ? odd : even) + '\n';
return out;
}
console.log('Even Case');
console.log( gridGen(8));
console.log('Odd Case');
console.log( gridGen(7));
If you are looking for another approach + efficiency try this

Having issues with clearing area around blank squares in minesweeper

Ok i finally got my minesweeper game made just needing one more thing if anyone could help me with. The part when you click on an unnumbered square and it will reveal some of the board. I have been playing around on this for sometime just drawing a blank. This is a simple minesweeper game just in java script. I have everything labeled where things should go to make it easier to find and i will bold it on where my code ive been working on is.
//Global
//store the value of each square
var gaValue = new Array(8)
for (i = 0; i <= 8; i++)
gaValue[i] = new Array(8)
for (i = 0; i <= 8; i++)
{
//loop through each item in those row
for (j = 0; j <= 8 ; j++)
gaValue[i][j] = 0
}
//Store the status of each square
var gaSquare = new Array(8)
for (j = 0; j <= 8; j++)
gaSquare[j] = new Array(8)
for (j = 0; j <= 8; j++)
{
//loop through each item in those row
for (i = 0; i <= 8 ; i++)
gaSquare[i][j] = "C"
}
//Track of whether the game is over or not (starts this with false)
var gbGameOver = false
function vInit()
{
var strHTML
var i
var j
strHTML = "<table style='margin-left:auto;margin-right:auto'>"
strHTML += "<tr><td colspan='8' style='text-align:center'>MineSweeper</td></tr>"
strHTML += "<tr><td colspan='8' style='text-align:center'><input type='button' id='btnNew' value='New Game' onclick='vNewGame()'></td></tr>"
//Loop through the rows to build the table of tiles
for (i = 0; i < 8; i++)
{
strHTML += "<tr>"
for (j = 0; j < 8; j++)
strHTML += '<td><img src="images/sqt0.png" id="square' + i + ', ' + j + '" onclick="vClick(' + i + ', ' + j + ')"/></td>';
strHTML += "<tr>";
}
strHTML += '<tr><td colspan="8" style="text-align:center"><textarea id="taOut" cols="18" rows="10"></textarea></td></tr>'
strHTML += "</table>"
frmGrid.innerHTML = strHTML
//Place bombs
var iBomb = 0
var iRow = Math.floor(Math.random() * 8)
var iCol = Math.floor(Math.random() * 8)
while (iBomb < 8)
{
while (gaValue[iRow][iCol] == 9)
{
iRow = Math.floor(Math.random() * 8)
iCol = Math.floor(Math.random() * 8)
}
gaValue[iRow][iCol] = 9
iBomb++
}
//Calculate clue values around mines
var iMine = 0
for (i = 0; i < 8; i++)
{
for (j = 0; j < 8; j++)
{
for (k = (i - 1) ; k <= (i + 1) ; k++)
for (m = (j - 1) ; m <= (j + 1) ; m++)
if (k >= 0 && k <= 9 && j >= 0 && j <= 9)
if (gaValue[k][m] == 9)
iMine++
if (gaValue[i][j] != 9)
gaValue[i][j] = iMine
iMine = 0
}
}
}
//Get the ID of the image I need to change
function vClick(iRow, iCol)
{
var gaSquare = "square" + iRow + ", " + iCol
var strOut = ""
gaSquare[iRow][iCol] = 'o';
document.getElementById(gaSquare).src = "images/" + gaValue[iRow][iCol] + ".png"
if (gaValue[iRow][iCol] == 9)
{
gbGameOver = true
strOut = "Game Over"
vOver()
}
else if (gaValue[iRow][iCol] == 0)
vZero(iRow, iCol)
document.getElementById('taOut').value = strOut
}
//GameOver
function vOver()
{
var i
var j
var strID;
for (i = 0; i < 8; i++)
for (j = 0; j < 8; j++) {
strID = "square" + i + ", " + j;
document.getElementById(strID).src = "images/" + gaValue[i][j] + ".png"
}
}
**//Clearing area
function vZero(iRow, iCol, i, j) {
for (i = iRow - 1; i <= iRow + 1; i++) {
for (j = iCol - 1; j <= iCol + 1; j++) {
if (k >= 0 && k <= 8 && j >= 0 && j <= 8)
vClick(i, j)
}**
//Start new game
function vNewGame() {
vInit()
}
//no menu on right click
function bIsRightButtonClicked(e) {
var rightclick = false
e = e || window.event
if (e.which) {
rightclick = (e.which == 3)
}
else if (e.button) {
rightclick = (e.button == 2)
}
return rightclick
}
}
}

I believe the main mistake is that you are referring to k inside vZero() when that variable is not defined. You also appear to be missing a closing curly bracket or two on that function.
Try changing that function to as follows:
//Clearing area
function vZero(iRow, iCol) {
for (var i = iRow - 1; i <= iRow + 1; i++) {
for (var j = iCol - 1; j <= iCol + 1; j++) {
if (i >= 0 && i <= 8 && j >= 0 && j <= 8) vClick(i, j);
}
}
}
You'll note that I changed the i and j parameters to be local variables, because they are only used by that function for the purposes of the for loops. You don't need to have them as parameters. Doing so only confuses other developers because that implies that you need to pass a value for them into the function for it to work, whereas you only need to pass in iRow and iCol. Does that make sense?

What I do in javascript to get my required result?

Here is my javascript code
for (var i = 1; i <= _MAXPAGECOUNT - 2; i++) {
e = document.getElementsByName("q" + i + "[]");
for (var j = 0; j <= e.length - 1; j++) {
if (e[j].checked) {
result = result + "," + i + ":" + e[j].value;
// break;
}
}}
The problem is this, it shows result like this 1:2,1:3,1:4,2:3,2:4,2:5
here in code i means question number and j means answer number, but I want to result as like this 1:2,3,4 ; 2:3,4,5

Try this
for (var i = 1; i <= _MAXPAGECOUNT - 2; i++) {
result = result+i+":";
e = document.getElementsByName("q" + i + "[]");
for (var j = 0; j <= e.length - 1; j++) {
if (e[j].checked) {
result = result + e[j].value;
// break;
}
}
if(i<_MAXPAGECOUNT - 2)
{
result = result+" ; ";
}
}