The return is not working (javascript) - javascript

The function is returning undefined why it's not returning the array length.even at the start of the code it's printing in the console but return is not working.
var resArr = [];
var p;
function persistence(num) {
resArr.push(num);
console.log(resArr);
console.log(resArr.length);
if (num > 10) {
var v = 1;
var x = num.toString();
var arr = [];
for (i = 0; i < x.length; i++) {
arr.push(x.charAt(i));
}
console.log(arr);
for (j = 0; j < arr.length; j++) {
var v = v * arr[j];
}
persistence(v);
} else {
return resArr.length - 1;
}
}

You're not returning in all cases.
Change
persistence(v);
to
return persistence(v);

Related

Why do I get an Uncaught TypeError: property 4 is undefined when looping through a 2d array?

So I am building Tetris. After creating an array, data, I am trying to implement gravity by checking
every string in an array if it's is "full" as well as being able the space below it being empty. However, it is giving me an error that suggests that something is undefined. The I tried a for loop and a for...of loop, as well as Googling it.Why do I get this error, and how can I fix it?
const editor = document.getElementById("edit");
var data = [];
function array(x, text) {
var y = [];
for (var i = 0; i < x - 1; i++) {
y.push(text);
}
return y;
}
for (var i = 0; i < 20; i++) {
data.push(array(10, "b"));
}
function draw() {
var j;
var i;
var dataOut = data;
for (i = 0; i < data.length; i++) {
for (j = 0; j < data[i].length; j++) {
if (data[i][j] == "a" && data[i + 1][j] == "b") {
if (i < data.length - 1) {
dataOut[i][j] = "b";
dataOut[i + 1][j] = "a";
}
}
}
}
data = dataOut;
console.log(data);
requestAnimationFrame(draw);
}
data[0][4] = "a";
requestAnimationFrame(draw);
with for-of-loop you iterate only objects/values of array and not indexes.
use only for-loop in order to use indexes
const editor = document.getElementById("edit");
var data = [];
function array(x, text) {
var y = [];
for (var i = 0; i < x - 1; i++) {
y.push(text);
}
return y;
}
for (var i = 0; i < 20; i++) {
data.push(array(10, "b"));
}
function draw() {
var dataOut = data;
for (let i = 0; i < data.length - 1; i++) { // logical error here
for (let j = 0; j < data.length; j++) {
if (data[i][j] == "a" && data[i + 1][j] == "b") {
if (i < data.length - 1) {
dataOut[i][j] = "b";
dataOut[i + 1][j] = "a";
}
}
}
}
data = dataOut;
console.log(data);
requestAnimationFrame(draw);
}
data[0][4] = "a";
requestAnimationFrame(draw);
A simple example of for-of-loop
const arr = ["aa","bb"]
for(let a of arr) console.log(a);
// will print
/*
aa
bb
*/
for(let a = 0; a < arr.length; a++) console.log(a);
// will print
/*
0
1
*/

JavaScript Function Insertion Sorting/ Function undefined

I am attempting to write a javascript file that has a insertion sort function, a function to check a sorted array and return true or false, and an insertion sort function that works from the end of the array index to the beginning.
Here is the code i have
function insertionSort(arr) {
for(var i = 1; i < arr.length; i++) {
var val = arr[i]; var j; for(j = i; j > 0 && arr[j-1] > val; j--) {
arr[j] = arr[j-1]; } arr[j] = val; }
}
function reverseInsertionSort(arr) {
for(var i = arr.length; i >1; i--)
{ var val = arr[i]; var j;
for(j = i; j > 0 && arr[j-1] > val; j--)
{ arr[j] = arr[j-1]; } arr[j] = val;
} }
var length = Math.floor(Math.random()*100)+1;
var arr = new Array();
for(let i = 0; i < length; i++) {
arr.push(Math.floor(Math.random()*10000)+1);
}
console.log(arr);
//function sortCheck(arr) {
//for( var i = 0 ; i < arr.length; i++){
// if(arr[i]>rr[i+1]){
// return false
// }
//}
//return true}
var sortedArr = insertionSort(arr);
console.log(sortedArr);
console.log("And with reverse \n");
var reverseSortedArr = reverseInsertionSort(arr);
console.log(reverseSortedArr);
//console.log(sortCheck(sortedArr));
The issue I am having right now is that sortedArr is undefined when output with console.log, it appears that the issue is that my function is "undefined" but seeing how i define it above, i dont understand how that is.
Your insertionSort function doesn't return a value, it modifies the array passed as an argument. Instead of var sortedArr = insertionSort(arr), just call insertionSort(arr) and then do console.log(arr).
You have to return arr from the function. It is not returning anything that's why you are getting undefined
function insertionSort(arr) {
for(var i = 1; i < arr.length; i++) {
var val = arr[i]; var j; for(j = i; j > 0 && arr[j-1] > val; j--) {
arr[j] = arr[j-1]; } arr[j] = val; }
return arr; }
function reverseInsertionSort(arr) {
for(var i = arr.length; i >1; i--)
{ var val = arr[i]; var j;
for(j = i; j > 0 && arr[j-1] > val; j--)
{ arr[j] = arr[j-1]; } arr[j] = val;
} return arr}
var length = Math.floor(Math.random()*100)+1;
var arr = new Array();
for(let i = 0; i < length; i++) {
arr.push(Math.floor(Math.random()*10000)+1);
}
console.log(arr);
var sortedArr = insertionSort(arr);
console.log(sortedArr);
console.log("And with reverse \n");
var reverseSortedArr = reverseInsertionSort(arr);
console.log(reverseSortedArr);
//console.log(sortCheck(sortedArr));
Make sure you return the array from the function(s). Since you currently are not, assigning the function to a variable would not yield any particular value.
function insertionSort(arr) {
for(var i = 1; i < arr.length; i++) {
var val = arr[i];
var j;
for(j = i; j > 0 && arr[j-1] > val; j--) {
arr[j] = arr[j-1];
}
arr[j] = val;
}
return arr
}

Find the index of the sub-array that does not contain a number

var array = [[2,3,4],[4,5,6],[2,3,9],[7,8,1]];
var number = 3;
If I have this nested array and this variable how do I return the index of the sub-arrays where the number is present. So the final result should be 1 and 3.
Try:
array.reduce((acc, subArr, i) => {
if (!subArr.includes(number)) {
acc.push(i);
}
return acc;
}, [])
The solution using Array.prototype.forEach() and Array.prototype.indexOf() functions:
var arr = [[2,3,4],[4,5,6],[2,3,9],[7,8,1]],
number = 3,
result = [];
arr.forEach(function(v,i){
if (v.indexOf(number) === -1) result.push(i);
});
console.log(result);
function X(a){
var r = [];
for(var i = o ; i < a.length; i++)
for(var j = o ; j < a[i].length; i++)
if(a[i][j] === number)
r.push(i);
return r;
}
i think this should do it. i have just written it here so might have some syntax errors
Since the question is super inconsistent, if you want the index of the subarrays that do have the number, do this:
var foundIndices = [];
for(var y = 0;y < array.length; y++) {
for(var x = 0;x < array[y].length; x++) {
if(array[y][x] == number) {
foundIndices[foundIndices.length] = y;
}
}
}
Otherwise, do this:
var foundIndices = [];
var found = false;
for(var y = 0;y < array.length; y++) {
found = false;
for(var x = 0;x < array[y].length; x++) {
if(array[y][x] == number) {
found = true;
}
}
if(found == false) {
foundIndices[foundIndices.length] = y;
}
}

How to program Pascal's Triangle in Javascript - confusion re Arrays

I'm having a little trouble with my attempt at this problem. Code Below:
function pasc(n){
var result = [[1]];
for (var row = 1; row < n; row++){
for (var col = 1; col <= row; col++){
result[row][col] = result[row - 1][col] + result[row - 1][col - 1];
}
}
return result;
}
pasc(10)
for (var i = 0; i < result.length; i++){
document.write(result[i]+"<br>");
}
It seems the problem hinges on assigning values to an array using an expression like myArray[1][1] = "foo"
I'm confused about this because I can do this: var myArray = []; myArray[4] = "foo" which seems to suggest that an element can be created at an arbitrary position in a 1 dimensional array, but not with 2 dimensions.
Any help with clearing up my misconceptions appreciated.
The Pascal's Triangle can be printed using recursion
Below is the code snippet that works recursively.
We have a recursive function pascalRecursive(n, a) that works up till the number of rows are printed. Each row is a element of the 2-D array ('a' in this case)
var numRows = 10,
triangle,
start,
stop;
// N is the no. of rows/tiers
// a is the 2-D array consisting of the row content
function pascalRecursive(n, a) {
if (n < 2) return a;
var prevRow = a[a.length-1];
var curRow = [1];
for (var i = 1; i < prevRow.length; i++) {
curRow[i] = prevRow[i] + prevRow[i-1];
}
curRow.push(1);
a.push(curRow);
return pascalRecursive(n-1, a); // Call the function recursively
}
var triangle = pascalRecursive(numRows, [[1]]);
for(var i = 0; i < triangle.length; i++)
console.log(triangle[i]+"\n");
JavaScript doesn't have two-dimensional arrays. What it does have is arrays that happen to contain other arrays. So, yes, you can assign a value to any arbitrary position in an array, and the array will magically make itself big enough, filling in any gaps with 'undefined'... but you can't assign a value to any position in a sub-array that you haven't explicitly created yet. You have to assign sub-arrays to the positions of the first array before you can assign values to the positions of the sub-arrays.
Replacing
for (var row = 1; row < n; row++){
for (var col = 1; col <= row; col++){
with
for (var row = 1; row < n; row++){
result[row] = [];
for (var col = 1; col <= row; col++){
should do it. Assuming all of your indexing logic is correct, anyway. You've got some problems there, too, since your initial array only contains a single value, so result[row][col] = result[row - 1][col] + result[row - 1][col - 1]; is accessing at least one cell that has never been defined.
Thanks Logan R. Kearsley. I have now solved it:
function pasc(n){
var result = [];
result[0] = [1];
result[1] = [1,1];
for (var row = 2; row < n; row++){
result[row] = [1];
for (var col = 1; col <= row -1; col++){
result[row][col] = result[row-1][col] + result[row-1][col-1];
result[row].push(1);
}
}
return result;
}
for (var i = 0; i < pasc(10).length; i++){
document.write(pasc(10)[i]+"<br>");
console.log(pasc(10)[i]+"<br>");
}
you can create Pascal's triangle using below code:
function pascal(n) {
var arr = [];
if (n == 1) {
arr[0] = [];
arr[0][0] = 1;
} else if (n == 2) {
arr[0] = [];
arr[0][0] = 1;
arr[1] = [];
arr[1][0] = 1;
arr[1][1] = 1;
} else if (n > 2) {
arr[0] = [];
arr[1] = [];
arr[0][0] = 1;
arr[1][0] = 1;
arr[1][1] = 1;
for (i = 2; i < n; i++) {
arr[i] = [];
arr[i][0] = 1;
for (j = 1; j < i; j++) {
arr[i][j] = arr[i - 1][j - 1] + arr[i - 1][j];
}
arr[i][j] = 1;
}
}
console.log(arr);
for (i = 0; i < arr.length; i++) {
console.log(arr[i].join(' '))
}
}
function pascal(n) {
var arr = [];
if (n == 1) {
arr[0] = [];
arr[0][0] = 1;
} else if (n == 2) {
arr[0] = [];
arr[0][0] = 1;
arr[1] = [];
arr[1][0] = 1;
arr[1][1] = 1;
} else if (n > 2) {
arr[0] = [];
arr[1] = [];
arr[0][0] = 1;
arr[1][0] = 1;
arr[1][1] = 1;
for (i = 2; i < n; i++) {
arr[i] = [];
arr[i][0] = 1;
for (j = 1; j < i; j++) {
arr[i][j] = arr[i - 1][j - 1] + arr[i - 1][j];
}
arr[i][j] = 1;
}
}
console.log(arr);
for (i = 0; i < arr.length; i++) {
console.log(arr[i].join(' '))
}
}
pascal(5)
This function will calculate Pascal's Triangle for "n" number of rows. It will create an object that holds "n" number of arrays, which are created as needed in the second/inner for loop.
function getPascalsTriangle(n) {
var arr = {};
for(var row = 0; row < n; row++) {
arr[row] = [];
for(var col = 0; col < row+1; col++) {
if(col === 0 || col === row) {
arr[row][col] = 1;
} else {
arr[row][col] = arr[row-1][col-1] + arr[row-1][col];
}
}
}
return arr;
}
console.log(getPascalsTriangle(5));
Floyd triangle
You can try the following code for a Floyd triangle
var prevNumber=1,i,depth=10;
for(i=0;i<depth;i++){
tempStr = "";j=0;
while(j<= i){
tempStr = tempStr + " " + prevNumber;
j++;
prevNumber++;
}
console.log(tempStr);
}
You can create arbitrary 2d arrays and store it in there and return the correct Pascal.
JavaScript does not have a special syntax for creating multidimensional arrays. A common workaround is to create an array of arrays in nested loops.
source
Here is my version of the solution
function pascal(input) {
var result = [[1], [1,1]];
if (input < 0) {
return [];
}
if (input === 0) {
return result[0];
}
for(var j = result.length-1; j < input; j++) {
var newArray = [];
var firstItem = result[j][0];
var lastItem = result[j][result[j].length -1];
newArray.push(firstItem);
for (var i =1; i <= j; i++) {
console.log(result[j][i-1], result[j][i]);
newArray.push(sum(result[j][i-1], result[j][i]));
}
newArray.push(lastItem);
result.push(newArray);
}
return result[input];
}
function sum(one, two) {
return one + two;
}
Here is the code i created for pascal triangle in javascript
'use strict'
let noOfCoinFlipped = 5
let probabiltyOfnoOfHead = 2
var dataStorer = [];
for(let i=0;i<=noOfCoinFlipped;i++){
dataStorer[i]=[];
for(let j=0;j<=i;j++){
if(i==0){
dataStorer[i][j] = 1;
}
else{
let param1 = (j==0)?0:dataStorer[i-1][j-1];
let param2 = dataStorer[i-1][j]?dataStorer[i-1][j]:0;
dataStorer[i][j] = param1+param2;
}
}
}
let totalPoints = dataStorer[noOfCoinFlipped].reduce((s,n)=>{return s+n;})
let successPoints = dataStorer[noOfCoinFlipped][probabiltyOfnoOfHead];
console.log(successPoints*100/totalPoints)
Here is the link as well
http://rextester.com/TZX59990
This is my solve:
function pascalTri(n){
let arr=[];
let c=0;
for(let i=1;i<=n;i++){
arr.push(1);
let len=arr.length;
if(i>1){
if(i>2){
for(let j=1;j<=(i-2);j++){
let idx=(len-(2*i)+j+2+c);
let val=arr[idx]+arr[idx+1];
arr.push(val);
}
c++;
}
arr.push(1);
}
}
return arr;
}
let pascalArr=pascalTri(7);
console.log(pascalArr);
here is the pattern for n = 3
#
##
###
here is js code to print this.
function staircase(n) {
for(var i=0 ; i<n ; i++) {
for(var j=n-1 ; j>i ; j--)
process.stdout.write(" ");
for(var k=0 ; k<=i; k++) {
process.stdout.write("#");
}
process.stdout.write("\n");
}
}
class PascalTriangle {
constructor(n) {
this.n = n;
}
factoriel(m) {
let result = 1;
if (m === 0) {
return 1;
}
while (m > 0) {
result *= m;
m--;
}
return result;
}
fill() {
let arr = [];
for (let i = 0; i < this.n; i++) {
arr.push([]);
}
for (let i = 0; i < arr.length; i++) {
for (let j = 0; j <= i; j++) {
arr[i].push(this.factoriel(i) / (this.factoriel(j) * this.factoriel(i - j)));
}
}
return arr;
}
}
var m = prompt("enter number:");
var arrMain = new Array();
for (var i = 0; i < m; i++) {
arrMain[i] = [];
}
for (var i = 0; i < m; i++) {
if (i == 0) {
arrMain[i] = [1];
} else if (i == 1) {
(arrMain[i]) = [1, 1];
} else {
for (var j = 0; j <= i; j++) {
if (j == 0 || j == arrMain[i - 1].length) {
arrMain[i][j] = 1;
} else {
arrMain[i][j] = arrMain[i - 1][j] + arrMain[i - 1][j - 1];
}
}
}
document.write(arrMain[i] + "<br>");
}
This is my take on this problem by gaining access to the previous row.
const generate = numRows => {
const triangle = [[1]]
for (let i = 1; i < numRows; i++) {
// Previous row
const previous = triangle[i - 1]
// Current row
const current = new Array(i + 1).fill(1)
// Populate the current row with the previous
// row's values
for (let j = 1; j < i; j++) {
current[j] = previous[j - 1] + previous[j]
}
// Add to triangle result
triangle.push(current)
}
return triangle
}

Interleave array elements

What is a fast and simple implementation of interleave:
console.log( interleave([1,2,3,4,5,6] ,2) ); // [1,4,2,5,3,6]
console.log( interleave([1,2,3,4,5,6,7,8] ,2) ); // [1,5,2,6,3,7,4,8]
console.log( interleave([1,2,3,4,5,6] ,3) ); // [1,3,5,2,4,6]
console.log( interleave([1,2,3,4,5,6,7,8,9],3) ); // [1,4,7,2,5,8,3,6,9]
This mimics taking the array and splitting it into n equal parts, and then shifting items off the front of each partial array in sequence. (n=2 simulates a perfect halving and single shuffle of a deck of cards.)
I don't much care exactly what happens when the number of items in the array is not evenly divisible by n. Reasonable answers might either interleave the leftovers, or even "punt" and throw them all onto the end.
function interleave( deck, step ) {
var copyDeck = deck.slice(),
stop = Math.floor(copyDeck.length/step),
newDeck = [];
for (var i=0; i<step; i++) {
for (var j=0; j<stop; j++) {
newDeck[i + (j*step)] = copyDeck.shift();
}
}
if(copyDeck.length>0) {
newDeck = newDeck.concat(copyDeck);
}
return newDeck;
}
It could be done with a counter instead of shift()
function interleave( deck, step ) {
var len = deck.length,
stop = Math.floor(len/step),
newDeck = [],
cnt=0;
for (var i=0; i<step; i++) {
for (var j=0; j<stop; j++) {
newDeck[i + (j*step)] = deck[cnt++];
}
}
if(cnt<len) {
newDeck = newDeck.concat(deck.slice(cnt,len));
}
return newDeck;
}
And instead of appending the extras to the end, we can use ceil and exit when we run out
function interleave( deck, step ) {
var copyDeck = deck.slice(),
stop = Math.ceil(copyDeck.length/step),
newDeck = [];
for (var i=0; i<step; i++) {
for (var j=0; j<stop && copyDeck.length>0; j++) {
newDeck[i + (j*step)] = copyDeck.shift();
}
}
return newDeck;
}
can i has prize? :-D
function interleave(a, n) {
var i, d = a.length + 1, r = [];
for (i = 0; i < a.length; i++) {
r[i] = a[Math.floor(i * d / n % a.length)];
}
return r;
}
according to my tests r.push(... is faster than r[i] = ... so do with that as you like..
note this only works consistently with sets perfectly divisible by n, here is the most optimized version i can come up with:
function interleave(a, n) {
var i, d = (a.length + 1) / n, r = [a[0]];
for (i = 1; i < a.length; i++) {
r.push(a[Math.floor(i * d) % a.length]);
}
return r;
}
O(n-1), can anyone come up with a log version? to the mathmobile! [spinning mathman logo]
Without for loops (I've added some checkup for the equal blocks):
function interleave(arr, blocks)
{
var len = arr.length / blocks, ret = [], i = 0;
if (len % 1 != 0) return false;
while(arr.length>0)
{
ret.push(arr.splice(i, 1)[0]);
i += (len-1);
if (i>arr.length-1) {i = 0; len--;}
}
return ret;
}
alert(interleave([1,2,3,4,5,6,7,8], 2));
And playground :) http://jsfiddle.net/7tC9F/
how about functional with recursion:
function interleave(a, n) {
function f(a1, d) {
var next = a1.length && f(a1.slice(d), d);
a1.length = Math.min(a1.length, d);
return function(a2) {
if (!a1.length) {
return false;
}
a2.push(a1.shift());
if (next) {
next(a2);
}
return true;
};
}
var r = [], x = f(a, Math.ceil(a.length / n));
while (x(r)) {}
return r;
}
Phrogz was pretty close, but it didn't interleave properly. This is based on that effort:
function interleave(items, parts) {
var len = items.length;
var step = len/parts | 0;
var result = [];
for (var i=0, j; i<step; ++i) {
j = i
while (j < len) {
result.push(items[j]);
j += step;
}
}
return result;
}
interleave([0,1,2,3], 2); // 0,2,1,3
interleave([0,1,2,3,4,5,6,7,8,9,10,11], 2) // 0,6,1,7,2,8,3,9,4,10,5,11
interleave([0,1,2,3,4,5,6,7,8,9,10,11], 3) // 0,4,8,1,5,9,2,6,10,3,7,11
interleave([0,1,2,3,4,5,6,7,8,9,10,11], 4) // 0,3,6,9,1,4,7,10,2,5,8,11
interleave([0,1,2,3,4,5,6,7,8,9,10,11], 5) // 0,2,4,6,8,10,1,3,5,7,9,11
Since I've been pushed to add my own answer early (edited to fix bugs noted by RobG):
function interleave(items,parts){
var stride = Math.ceil( items.length / parts ) || 1;
var result = [], len=items.length;
for (var i=0;i<stride;++i){
for (var j=i;j<len;j+=stride){
result.push(items[j]);
}
}
return result;
}
try this one:
function interleave(deck, base){
var subdecks = [];
for(count = 0; count < base; count++){
subdecks[count] = [];
}
for(var count = 0, subdeck = 0; count < deck.length; count++){
subdecks[subdeck].push(deck[count]);
subdeck = subdeck == base - 1? 0 : subdeck + 1;
}
var newDeck = [];
for(count = 0; count < base; count++){
newDeck = newDeck.concat(subdecks[count]);
}
return newDeck;
}

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