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I am new to javascript and trying to loop through an array to set each element equal to a random number. I am wondering why this works:
function randomize() {
for (let i = 1; i < 16; i++) {
let random = Math.floor(Math.random() * 30);
document.getElementById(i).style.paddingTop = random + "%";
}
}
but when I am trying to use an array instead of a variable, doesn't:
function randomize() {
const sortArray = [];
for (let i = 1; i < 16; i++) {
let sortArray[i] = Math.floor(Math.random() * 30);
document.getElementById(i).style.paddingTop = sortArray[i] + "%";
}
}
This is a syntax error. You should remove let in the array[i] declaration
function randomize() {
const sortArray = [];
for (let i = 1; i < 16; i++) {
sortArray[i] = Math.floor(Math.random() * 30);
document.getElementById(i).style.paddingTop = sortArray[i] + "%";
}
}
You are declaring sortArray again.
You have already declared sortArray as
const sortArray=[]; //sort array is already declared here
for (let i = 1; i < 16; i++) {
sortArray[i] = Math.floor(Math.random() * 30); //No need to declare again
document.getElementById(i).style.paddingTop = sortArray[i] + "%";
}}
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Closed 3 years ago.
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I'm supposed to get the multiplication value of the multi-dimensional array. but I am getting '1' as output whatever values being changed in array.
function arrayMultiplyer(arr){
var multi = 1;
for(var i=0;i < arr.length; i++){
for(var j =0; j<arr[i];j++){
multi *= arr[i][j];
}
}
return multi;
}
var multi = arrayMultiplyer([[2,33],[33,2],[5,6,9]]);
console.log(multi);
You need to check arr[i].length in the j loop.
function arrayMultiplyer(arr){
var multi = 1;
for(var i=0;i < arr.length; i++){
for(var j =0; j<arr[i].length;j++){ // you need to check arr[i].length here
multi *= arr[i][j];
}
}
return multi;
}
var multi = arrayMultiplyer([[2,33],[33,2],[5,6,9]]);
console.log(multi);
You can simply do this in two lines.
function arrayMultiplyer(arr){
let flattenedArray = arr.flat();
return flattenedArray.reduce((x, y) => x * y);
}
var multi = arrayMultiplyer([[2,33],[33,2],[5,6,9]]);
console.log(multi);
An alternative solution using .reduce()
function arrayMultiplier(arr) {
return arr.reduce((tot,arr2) =>
arr2.reduce((subTot, n) =>
subTot * n
, tot)
, 1);
}
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I've been reading about ES6 Let keyword vs existing var keyword.
I've got few questions. I understand that "scoping" is the only difference between let and var but what does it mean for the big picture?
function allyIlliterate() {
//tuce is *not* visible out here
for( let tuce = 0; tuce < 5; tuce++ ) {
//tuce is only visible in here (and in the for() parentheses)
};
//tuce is *not* visible out here
};
function byE40() {
//nish *is* visible out here
for( var nish = 0; nish < 5; nish++ ) {
//nish is visible to the whole function
};
//nish *is* visible out here
};
Now my questions:
Does let posses any memory(/performance) advantage over var?
Other than browser support, what are the reasons why i should be using let over var?
Is it safe to start using let now over var in my code workflow?
Thanks,
R
let is much slower than var in node.js. Version v6.3.0 anyway. Sometimes this is dramatic. The code below is about three times slower if you replace var with let:
function collatz() {
var maxsteps = 0;
var maxval = 0;
var x = 1;
var n;
var steps;
while (x < 1000000) {
steps = 0;
n = x;
while (n > 1) {
if (n & 1)
n = 3*n + 1;
else
n = n / 2;
steps += 1;
}
if (steps > maxsteps) {
maxsteps = steps;
maxval = x;
}
x += 1;
}
console.log(maxval + ' - ' + maxsteps + ' steps');
}
collatz();
They asked me to learn JavaScript for work, so I'm doing some of the solutions on Project Euler to help me learn.
My solution for problem 8 works for the 4 number example they give, if I change the 13s to 4s, but it doesn't get the right answer for 13 digits as the question wants.
I solved this problem forever ago in C and don't remember it giving me this much trouble. Am I doing something wrong with JavaScript or is this a error with my code? In either case, please point me in the right direction.
My code:
var numbas = "\
73167176531330624919225119674426574742355349194934\
96983520312774506326239578318016984801869478851843\
85861560789112949495459501737958331952853208805511\
12540698747158523863050715693290963295227443043557\
66896648950445244523161731856403098711121722383113\
62229893423380308135336276614282806444486645238749\
30358907296290491560440772390713810515859307960866\
70172427121883998797908792274921901699720888093776\
65727333001053367881220235421809751254540594752243\
52584907711670556013604839586446706324415722155397\
53697817977846174064955149290862569321978468622482\
83972241375657056057490261407972968652414535100474\
82166370484403199890008895243450658541227588666881\
16427171479924442928230863465674813919123162824586\
17866458359124566529476545682848912883142607690042\
24219022671055626321111109370544217506941658960408\
07198403850962455444362981230987879927244284909188\
84580156166097919133875499200524063689912560717606\
05886116467109405077541002256983155200055935729725\
71636269561882670428252483600823257530420752963450";
var biggestProduct = 0;
var currentProduct = 0;
var currentNumbas = {};
function product (proddedNumbas){
var productHolda = 1;
for (var i = 0; i < 13; i++)
productHolda *= proddedNumbas[i];
return productHolda;
}
for (var j = 0; j < 1000; j++)
for (var i = 0; i < 13; i++){
currentNumbas[i] = numbas[j+i];
currentProduct = product(currentNumbas);
if (currentProduct > biggestProduct)
biggestProduct = currentProduct;
}
console.log(biggestProduct);
Your loop should be
for (var j = 0; j < 1000; j++) {
for (var i = 0; i < 13; i++) {
currentNumbas[i] = numbas[j+i];
currentProduct = product(currentNumbas);
}
if (currentProduct > biggestProduct)
biggestProduct = currentProduct;
}
You just needed to move the if clause outside of the inner loop; this compares the product after it is complete.
This gives the expected answer 23514624000.
I'm really sorry if anything like this has been posted here before but I couldn't find anything, I'm kinda new to the site still!
So for a while now I've been learning a bit about game development through html5 and javascript and I stumbled upon making tileset maps, I now have a tileset and an 2D array that I want to put certain tiles in (the number varies between 6 and 10 in this case).
I figured it could be a cool function to make the map choose between a small set of similar tiles so I don't have to specifically number every tile in the array(just define the type)
The method I have currently is probably the best for being able to define types but I want something that looks a bit cleaner and/or information to why my "cleaner" version dosen't work.
var ground = [
[tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile()],
[tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile()],
[tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile()],
[tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile()],
[tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile()],
[tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile()],
[tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile()],
[tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile()],
[tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile(),tile()]];
function tile() {
var y = (Math.random() * 5 | 0) + 6;
return y;
}
This is the code I've been using so far, I have to edit every element of the code with the tile() function to get a random number in each one, what I wanted to have was something like this:
for (var i = 0 ; i < 15; i++) {
for (var j = 0; j < 9; j++) {
ground[[i],[j]] = (Math.random() * 5 | 0) + 6;
}
}
to fill the array without having to add the function to each spot.
I have a feeling that I'm missing a return function or something along those lines but honestly I have no idea.
You were thinking in the right direction but there are some errors in your code ;)
You have to initialize the array first before you can push elements into it.
And you were counting i++ twice
Javascript
var ground = []; // Initialize array
for (var i = 0 ; i < 15; i++) {
ground[i] = []; // Initialize inner array
for (var j = 0; j < 9; j++) { // i++ needs to be j++
ground[i][j] = (Math.random() * 5 | 0) + 6;
}
}
Maybe even better (reusable)
function createGround(width, height){
var result = [];
for (var i = 0 ; i < width; i++) {
result[i] = [];
for (var j = 0; j < height; j++) {
result[i][j] = (Math.random() * 5 | 0) + 6;
}
}
return result;
}
// Create a new ground with width = 15 & height = 9
var ground = createGround(15, 9);
Here's a quick example. I've created a function that will take in a width and height parameter and generate the size requested. Also I placed your tile function inside generate ground to keep it private, preventing other script from invoking it.
var ground = generateGround(10, 10); //Simple usage
function generateGround(height, width)
{
var ground = [];
for (var y = 0 ; y < height; y++)
{
ground[y] = [];
for (var x = 0; x < width; x++)
{
ground[y][x] = tile();
}
}
return ground;
function tile()
{
return (Math.random() * 5 | 0) + 6;
}
}
http://jsbin.com/sukoyute/1/edit
Try removing the comma from...
ground[[i],[j]] = (Math.random() * 5 | 0) + 6;
...in your 'clean' version. Also, your incrementing 'i' in both for loops:
for (var i = 0 ; i < 15; i++) {
for (var j = 0; j < 9; i++) {
Hopefully these changes make it work for you :)