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Adding asterisks to array?

I'm trying to add elements as asterisks inside array based on number of elements. Basically If numberOfRows is 3 then I want this output:
[
' * ',
' *** ',
'*****'
]
I'm struggling on setting asterisks using the index. Can anyone point me in the right direction? Thanks a lot!
Here's my code:
function myFunction(numberOfRows) {
var arr = [];
var value = "";
var asterisk = "*"; // Need to update this based on number of rows
for (var i = 1; i <= numberOfRows; i++) {
value += asterisk;
arr.push(value);
}
return arr;
}

Got it working! Here's a perfect solution.
function myFunction(n) {
let arr = [];
for(let f = 1; f <= n; f++) {
arr.push(' '.repeat(n - f) + '*'.repeat(f + f - 1) + ' '.repeat(n - f));
}
return arr;
}
console.log(myFunction(3));

Try something like this;
function myFunction(numberOfRows) {
var arr = [];
var value = "";
var slots = numberOfRows * 2 - 1;
var spaceSlots, asteriskSlots, spaces;
for (var i = 0; i < numberOfRows; i++) {
asteriskSlots = i * 2 + 1;
spaceSlots = Math.floor((slots - asteriskSlots)/2);
spaces = new Array(spaceSlots).fill(' ').join('');
value = spaces + '*'.repeat(asteriskSlots) + spaces;
arr.push(value);
}
return arr;
}
console.log(myFunction(20));

Array loop in javascript

I try to develop a simple program that prints all numbers in between 1 and 100 that divide by 3 without any residual and calculate the total sum
I did it with for loop:
var sum = 0;
for (var i = 3; i <= 100; i = i + 3) {
document.write("<br/>" + i);
sum = sum + i;
}
document.write("<br/>sum = " + sum); //1683
But I failed when I wanted to do it with array:
var numbers = [];
var sum = 0;
for (var i = 0; i <= 100; i = i + 3) {
numbers[i - 1] = i;
}
for (var index = 0; index < 100; index++) {
document.write("<br/>" + numbers[index]);
sum = sum + i;
}
document.write("<br/>sum = " + sum);

Use it like this,
Array indexes should start from 0, that is why I have introduced another variable j=0
var numbers = [];
var sum = 0;
for (var i = 0, j = 0; i <= 100; i = i + 3, ++j) {
numbers[j] = i;
}
Update
First Issue:
In your code, ie. below code of yours,
for (var i = 0; i <= 100; i = i + 3) {
numbers[i - 1] = i;
}
In the first iteration,
i = 0;
numbers[0-1] = i // i.e numbers[-1] = 0;
and in your second loop, you are starting the index from 0
for (var index = 0; index < 100; index++) {
Second issue:
Also, if you don't use a sequential counter to fill the Array, you will end with undefined values for the ones you did not fill.
If you notice, the output after the loop, it says numbers.length = 99 which is wrong it will not have that many items in it.
Third Issue:
In below code, even if you introduce a sequential counter, this is still wrong
for (var i = 0; i <= 100; i = i + 3) {
numbers[i - 1] = i;
}
because i should start with 3 instead of 0, otherwise you will end up with 34 elements in the array because numbers[0] will be 0;
Fourth Issue:
In this code,
for (var index = 0; index < 100; index++) {
document.write("<br/>" + numbers[index]);
sum = sum + i;
}
You don't actually have to loop it till 100, you already have the numbers array filled, so you just need to use numbers.length, like this
var len = numbers.length;
for (var index = 0; index < len; index++) {
document.write("<br/>" + numbers[index]);
sum = sum + i;
}
A better way to write this
var numbers = [];
for (var i = 3, j=0; i <= 100; i = i + 3, j++) {
numbers[j] = i;
}
var sum = numbers.reduce((a, b) => a+b);
console.log(sum);
The line var sum = numbers.reduce((a, b) => a+b); uses Array.reduce() method.

adding number to array
var numbers = [];
for(var i = 3; i <= 100; i = i +3){
numbers.push(i);
}
summation and printing values
var sum = 0;
for (var i = 0; i < numbers.length; i++) {
document.write("<br/>" + numbers[i]);
sum = sum + numbers[i];
}
document.write("<br/>sum = " + sum); //1683

There are few issues in your code.
for (var i = 0; i <= 100; i = i + 3) {
numbers[i - 1] = i;
}
1: array is 0 based. so first insertion into the array goes for a toss.
2: the number array created will have skipping index like 3, 6 ,9
for (var index = 0; index < 100; index++) {
document.write("<br/>" + numbers[index]);
sum = sum + i;
}
3: Here you are iterating index till 100 , you should iterate it till the length of the numbers array only.
when index is 1,2
number[index] will become undefined.
4: sum = sum + i (i ??????)
You should try like this or you can also use push()
var numbers = [];
var sum = 0;
for (var i = 0,j=0; i <= 100; i = i + 3, j= j+1) {
numbers[j] = i; // array is 0 based.
}
for (var index = 0; index < numbers.length; index++) {
document.write("<br/>" + numbers[index]);
sum = sum + numbers[index];
}
document.write("<br/>sum = " + sum);

Indexes in an array begin with zero.
for (var i = 0; i <= 100; i = i + 3) {
numbers[i - 1] = i; // In the first iteration, there will be numbers[-1] = i;
}

You have several issues i suppose.
var numbers = [];
var sum = 0;
for (var i = 0; i <= 100; i = i + 3) {
numbers.push(i);
}
for (var index = 0; index < numbers.length; index++) {
document.write("<br/>" + numbers[index]);
sum = sum + i;
}
document.write("<br/>sum = " + sum);
Also for array you can use:
for (var i in array) {
console.log(array[i]);
}
And I'm pretty sure, that array of number sequence is absolutely useless, if there is no other information in it.

Try this
var numbers = [];
var sum = 0;
for (var i = 0; i <= 100; i = i + 3) {
numbers[(i-3)/3] = i;
}
for (var index = 0; index < numbers.length; index++) {
document.write("<br/>" + numbers[index]);
sum = sum + numbers[index];
}
document.write("<br/>sum = " + sum);
Here is the fiddle i tried
https://jsfiddle.net/4ncgnd7c/

This should work using a single loop
var numbers = [];
var sum = 0;
for (var i = 3; i <= 100; i = i + 3) {
numbers[i] = i;
document.write("<br/>" + i);
sum = sum + i;
}
document.write("<br/>sum = " + sum);

Longest palindrome in a string

I wrote the following function to find the longest palindrome in a string. It works fine but it won't work for words like "noon" or "redder". I fiddled around and changed the first line in the for loop from:
var oddPal = centeredPalindrome(i, i);
to
var oddPal = centeredPalindrome(i-1, i);
and now it works, but I'm not clear on why. My intuition is that if you are checking an odd-length palindrome it will have one extra character in the beginning (I whiteboarded it out and that's the conclusion I came to). Am I on the right track with my reasoning?
var longestPalindrome = function(string) {
var length = string.length;
var result = "";
var centeredPalindrome = function(left, right) {
while (left >= 0 && right < length && string[left] === string[right]) {
//expand in each direction.
left--;
right++;
}
return string.slice(left + 1, right);
};
for (var i = 0; i < length - 1; i++) {
var oddPal = centeredPalindrome(i, i);
var evenPal = centeredPalindrome(i, i);
if (oddPal.length > result.length)
result = oddPal;
if (evenPal.length > result.length)
result = evenPal;
}
return "the palindrome is: " + result + " and its length is: " + result.length;
};
UPDATE:
After Paul's awesome answer, I think it makes sense to change both variables for clarity:
var oddPal = centeredPalindrome(i-1, i + 1);
var evenPal = centeredPalindrome(i, i+1);

You have it backwards - if you output the "odd" palindromes (with your fix) you'll find they're actually even-length.
Imagine "noon", starting at the first "o" (left and right). That matches, then you move them both - now you're comparing the first "n" to the second "o". No good. But with the fix, you start out comparing both "o"s, and then move to both "n"s.
Example (with the var oddPal = centeredPalindrome(i-1, i); fix):
var longestPalindrome = function(string) {
var length = string.length;
var result = "";
var centeredPalindrome = function(left, right) {
while (left >= 0 && right < length && string[left] === string[right]) {
//expand in each direction.
left--;
right++;
}
return string.slice(left + 1, right);
};
for (var i = 0; i < length - 1; i++) {
var oddPal = centeredPalindrome(i, i + 1);
var evenPal = centeredPalindrome(i, i);
if (oddPal.length > 1)
console.log("oddPal: " + oddPal);
if (evenPal.length > 1)
console.log("evenPal: " + evenPal);
if (oddPal.length > result.length)
result = oddPal;
if (evenPal.length > result.length)
result = evenPal;
}
return "the palindrome is: " + result + " and its length is: " + result.length;
};
console.log(
longestPalindrome("nan noon is redder")
);

This will be optimal if the largest palindrome is found earlier.
Once its found it will exit both loops.
function isPalindrome(s) {
//var rev = s.replace(/\s/g,"").split('').reverse().join(''); //to remove space
var rev = s.split('').reverse().join('');
return s == rev;
}
function longestPalind(s) {
var maxp_length = 0,
maxp = '';
for (var i = 0; i < s.length; i++) {
var subs = s.substr(i, s.length);
if (subs.length <= maxp_length) break; //Stop Loop for smaller strings
for (var j = subs.length; j >= 0; j--) {
var sub_subs = subs.substr(0, j);
if (sub_subs.length <= maxp_length) break; // Stop loop for smaller strings
if (isPalindrome(sub_subs)) {
maxp_length = sub_subs.length;
maxp = sub_subs;
}
}
}
return maxp;
}

Here is another take on the subject.
Checks to make sure the string provided is not a palindrome. If it is then we are done. ( Best Case )
Worst case 0(n^2)
link to
gist
Use of dynamic programming. Break each problem out into its own method, then take the solutions of each problem and add them together to get the answer.
class Palindrome {
constructor(chars){
this.palindrome = chars;
this.table = new Object();
this.longestPalindrome = null;
this.longestPalindromeLength = 0;
if(!this.isTheStringAPalindrome()){
this.initialSetupOfTableStructure();
}
}
isTheStringAPalindrome(){
const reverse = [...this.palindrome].reverse().join('');
if(this.palindrome === reverse){
this.longestPalindrome = this.palindrome;
this.longestPalindromeLength = this.palindrome.length;
console.log('pal is longest', );
return true;
}
}
initialSetupOfTableStructure(){
for(let i = 0; i < this.palindrome.length; i++){
for(let k = 0; k < this.palindrome.length; k++){
this.table[`${i},${k}`] = false;
}
}
this.setIndividualsAsPalindromes();
}
setIndividualsAsPalindromes(){
for(let i = 0; i < this.palindrome.length; i++){
this.table[`${i},${i}`] = true;
}
this.setDoubleLettersPlaindrome();
}
setDoubleLettersPlaindrome(){
for(let i = 0; i < this.palindrome.length; i++){
const firstSubstring = this.palindrome.substring(i, i + 1);
const secondSubstring = this.palindrome.substring(i+1, i + 2);
if(firstSubstring === secondSubstring){
this.table[`${i},${i + 1}`] = true;
if(this.longestPalindromeLength < 2){
this.longestPalindrome = firstSubstring + secondSubstring;
this.longestPalindromeLength = 2;
}
}
}
this.setAnyPalindromLengthGreaterThan2();
}
setAnyPalindromLengthGreaterThan2(){
for(let k = 3; k <= this.palindrome.length; k++){
for(let i = 0; i <= this.palindrome.length - k; i++){
const j = i + k - 1;
const tableAtIJ = this.table[`${i+1},${j-1}`];
const stringToCompare = this.palindrome.substring(i, j +1);
const firstLetterInstringToCompare = stringToCompare[0];
const lastLetterInstringToCompare = [...stringToCompare].reverse()[0];
if(tableAtIJ && firstLetterInstringToCompare === lastLetterInstringToCompare){
this.table[`${i},${j}`] = true;
if(this.longestPalindromeLength < stringToCompare.length){
this.longestPalindrome = stringToCompare;
this.longestPalindromeLength = stringToCompare.length;
}
}
}
}
}
printLongestPalindrome(){
console.log('Logest Palindrome', this.longestPalindrome);
console.log('from /n', this.palindrome );
}
toString(){
console.log('palindrome', this.palindrome);
console.log(this.table)
}
}
// const palindrome = new Palindrome('lollolkidding');
// const palindrome = new Palindrome('acbaabca');
const palindrome = new Palindrome('acbaabad');
palindrome.printLongestPalindrome();
//palindrome.toString();

function longestPalindrome(str){
var arr = str.split("");
var endArr = [];
for(var i = 0; i < arr.length; i++){
var temp = "";
temp = arr[i];
for(var j = i + 1; j < arr.length; j++){
temp += arr[j];
if(temp.length > 2 && temp === temp.split("").reverse().join("")){
endArr.push(temp);
}
}
}
var count = 0;
var longestPalindrome = "";
for(var i = 0; i < endArr.length; i++){
if(count >= endArr[i].length){
longestPalindrome = endArr[i-1];
}
else{
count = endArr[i].length;
}
}
console.log(endArr);
console.log(longestPalindrome);
return longestPalindrome;
}
longestPalindrome("abracadabra"));

let str = "HYTBCABADEFGHABCDEDCBAGHTFYW12345678987654321ZWETYGDE";
let rev = str.split("").reverse().join("").trim();
let len = str.length;
let a="";
let result = [];
for(let i = 0 ; i < len ; i++){
for(let j = len ; j > i ; j--){
a = rev.slice(i,j);
if(str.includes(a)){
result.push(a);
break;
}
}
}
result.sort((a,b) => { return b.length - a.length})
let logPol = result.find((value)=>{
return value === value.split('').reverse().join('') && value.length > 1
})
console.log(logPol);

function longest_palindrome(s) {
if (s === "") {
return "";
}
let arr = [];
let _s = s.split("");
for (let i = 0; i < _s.length; i++) {
for (let j = 0; j < _s.length; j++) {
let word = _s.slice(0, j + 1).join("");
let rev_word = _s
.slice(0, j + 1)
.reverse()
.join("");
if (word === rev_word) {
arr.push(word);
}
}
_s.splice(0, 1);
}
let _arr = arr.sort((a, b) => a.length - b.length);
for (let i = 0; i < _arr.length; i++) {
if (_arr[arr.length - 1].length === _arr[i].length) {
return _arr[i];
}
}
}
longest_palindrome('bbaaacc')
//This code will give you the first longest palindrome substring into the string

var longestPalindrome = function(string) {
var length = string.length;
var result = "";
var centeredPalindrome = function(left, right) {
while (left >= 0 && right < length && string[left] === string[right]) {
//expand in each direction.
left--;
right++;
}
return string.slice(left + 1, right);
};
for (var i = 0; i < length - 1; i++) {
var oddPal = centeredPalindrome(i, i + 1);
var evenPal = centeredPalindrome(i, i);
if (oddPal.length > 1)
console.log("oddPal: " + oddPal);
if (evenPal.length > 1)
console.log("evenPal: " + evenPal);
if (oddPal.length > result.length)
result = oddPal;
if (evenPal.length > result.length)
result = evenPal;
}
return "the palindrome is: " + result + " and its length is: " + result.length;
};
console.log(longestPalindrome("n"));
This will give wrong output so this condition need to be taken care where there is only one character.

public string LongestPalindrome(string s) {
return LongestPalindromeSol(s, 0, s.Length-1);
}
public static string LongestPalindromeSol(string s1, int start, int end)
{
if (start > end)
{
return string.Empty;
}
if (start == end)
{
char ch = s1[start];
string s = string.Empty;
var res = s.Insert(0, ch.ToString());
return res;
}
if (s1[start] == s1[end])
{
char ch = s1[start];
var res = LongestPalindromeSol(s1, start + 1, end - 1);
res = res.Insert(0, ch.ToString());
res = res.Insert(res.Length, ch.ToString());
return res;
}
else
{
var str1 = LongestPalindromeSol(s1, start, end - 1);
var str2 = LongestPalindromeSol(s1, start, end - 1);
if (str1.Length > str2.Length)
{
return str1;
}
else
{
return str2;
}
}
}

This is in JS ES6. much simpler and works for almost all words .. Ive tried radar, redder, noon etc.
const findPalindrome = (input) => {
let temp = input.split('')
let rev = temp.reverse().join('')
if(input == rev){
console.log('Palindrome', input.length)
}
}
//i/p : redder
// "Palindrome" 6

$.inArray() jQuery function

I can not figure out why this is not working, should be returning an array with four distinct values, but it doesn't
$(document).ready(function (e) {
var randomNumbers = new Array();
for (var i = 0; i < 4; i++) {
randomNumbers[i] = Math.floor((Math.random() * 9) + 1);
while ($.inArray(randomNumbers[i], randomNumbers) !== -1) {
randomNumbers[i] = Math.floor((Math.random() * 9) + 1);
}
}
for (var i = 0; i < randomNumbers.length; i++) {
if ($('#output').html() !== '') {
var existingOutput = $('#output').html();
$('#output').html(existingOutput + randomNumbers[i]);
} else {
$('#output').html(randomNumbers[i]);
}
}
});

Can cut out the if and the second loop by appending the joined array
$(document).ready(function (e) {
var randomNumbers = new Array();
for (var i = 0; i < 4; i++) {
var ran =newNum();
/* unique check*/
while ( $.inArray( ran, randomNumbers) >-1){
ran=newNum();
}
randomNumbers.push(ran)
}
$('#output').append( randomNumbers.join(''))
});
function newNum(){
return Math.floor((Math.random() * 9) + 1);
}
Alternate solution using a shuffle method ( found in this post ):
var a=[1,2,3,4,5,6,7,8,9];
function Shuffle(o) {
for(var j, x, i = o.length; i; j = parseInt(Math.random() * i), x = o[--i], o[i] = o[j], o[j] = x);
return o;
};
$('#output').append( Shuffle(a).splice(0,4).join(''))

If you generate a number and put it in the array, don't you think that $.inArray() will tell you so?
Your while loop is guaranteed to hang. A member of the array (randomNumbers[i]) is always, of course, going to be in the array. In fact $.inArray() when called to see if randomNumbers[i] is in the array will return i (if it's nowhere else, which in this case it can't be). Your loop won't get past the first number, so it'll just be 0.

I don't understand the point of your while loop. inArray only returns -1 if the value isn't found, which it will always be found, so you're just creating an infinite loop for yourself that will keep resetting the random number generated.
If you're just trying to add four random numbers to a div, this worked for me:
$(document).ready(function (e) {
var randomNumbers = new Array();
for (var i = 0; i < 4; i++) {
randomNumbers[i] = Math.floor((Math.random() * 9) + 1);
}
for (var i = 0; i < randomNumbers.length; i++) {
if ($('#output').html() !== '') {
var existingOutput = $('#output').html();
$('#output').html(existingOutput + randomNumbers[i]);
} else {
$('#output').html(randomNumbers[i]);
}
}
});
Further refactored:
$(document).ready(function (e) {
var randomNumbers = new Array();
for (var i = 0; i < 4; i++) {
randomNumbers[i] = Math.floor((Math.random() * 9) + 1);
}
for (var i = 0; i < randomNumbers.length; i++) {
$('#output').append(randomNumbers[i]);
}
});

How to count a javascript array and get output like this?

i have a array like this
["5763.34", "5500.00", "5541.67", "5541.67"]
i want to count similar values and get a out put like
(1 * 5763.34) + (1 * 5500.00) + (2 * 5541.67)
any idea how to do this?

Count values:
var array = ["5763.34", "5500.00", "5541.67", "5541.67"]
var counts = {};
for (var i = 0; i < array.length; ++i) {
var val = array[i];
if (val in counts) {
counts[val]++;
} else {
counts[val] = 1;
}
}
Print them:
var strings = [];
for (var k in counts) {
strings.push('(' + counts[k] + ' * ' + k + ')');
}
alert(strings.join(' + '));
Try it here: http://jsfiddle.net/k46kL/1

do it like this
sum = 0
for(i=0; i< array.length; i++){
sum += array[i] * (i+1)
}