Develop Reference

javascript: clicking numerical boxes - increment not working

using the code below, I've created a grid of buttons, 5x5, with random 1-25 numbers assigned to each button. They are to be clicked in numerical order, each's background turns red when clicked in the correct order. I can't use a global variable for this prompt. Without a global variable, I can't figure out how to increment the correctNumbers function which checks whether the right number is clicked each time. I think I'm missing something, a js function or something that would enable an incrementing variable declared within the incrementing function. I'm not looking for the whole explanation, just tips on functions i might not know about, and whether or not what i'm trying to do just isn't logicly possible.
<div id="numbers" class="hidden"></div>
<div id="youWon" class="hidden">You Won!</div>
The relevant JS:
... /**
* Gives the numbers a random order
* the "Fisher-Yates shuffle" found at: https://www.frankmitchell.org/2015/01/fisher-yates/
* #param {*} array
*/
const shuffle = (array) => {
let i = 0,
j = 0,
temp = null
for (i = array.length - 1; i > 0; i -= 1) {
j = Math.floor(Math.random() * (i + 1))
temp = array[i]
array[i] = array[j]
array[j] = temp
}
}
/**
* Generates an array of numbers 1-25
*/
const generateNums = () => {
document.getElementById("youWon").classList.toggle("hidden", "visible");
const numberArray = [];
for (let a = 1; a <= 25; a++) {
numberArray.push(a);
}
shuffle(numberArray);
let numEl = document.getElementById('numbers'); //write into html div id "numbers"
for (let b = 0; b <= 24; b++) { //loop to create button array
let newBtn = document.createElement('button'); //create buttons
newBtn.className = 'number'; //assign newBtns 'number' class
newBtn.innerText = numberArray[b]; //assign numbers to each button
numEl.appendChild(newBtn); //match with number elements in "numbers" array
newBtn.addEventListener("click", onNumberClick) //create function trigger
}
}
/**
* Creates a function to decide correct and incorrect clicks
* When a user clicks a number, if it is the next number in order, then it turns a different color for the remainder of the test
* If it is the wrong number, nothing happens
* #param {*} event
*/
const incrementNum = (correctNumber) => {
correctNumber++;
}
const onNumberClick = (event) => {
let correctNumber = 1; //start at 1
let numberVal = event.target; //apply it to clicks on the numbers
if (Number(numberVal.innerHTML) + 1 == incrementNum(correctNumber)) {
incrementNum(correctNumber);
numberVal.classList.add("red");
}
if (correctNumber == 26) {
document.getElementById("youWon").classList.toggle("visible"); //show win message if 25 is the last button and gets clicked
}
}

I would suggest that you count the number of elements in the DOM that have the class "red" and add 1... checking if the innerHTML is equal to that number to get the sequence right. So, instead of this:
if (Number(numberVal.innerHTML) + 1 == incrementNum(correctNumber)) {
incrementNum(correctNumber);
numberVal.classList.add("red");
}
You can have something like this:
if(Number(numberVal.innerHTML) == document.getElementsByClassName('red').length + 1) {
numberVal.classList.add("red");
}

List array elements, one by one, with a click of a button

I am new to Javascript and working with the basics. I am wanting to create an array whose individual elements are randomly drawn, one at a time, with a click of a button, until all array elements are displayed on the screen. The code I have is almost there. But the issue is that when it runs, it always grabs 2 elements on the first button click, rather than 1. It runs well for the remaining elements. Sure would appreciate some insight to this problem. Thank you.
var myArray=['1','2','3','4','5','6','7']
var text = "";
var i;
function RandomDraw() {
for(i = 0; i < myArray.length; i+=text) {
var ri = Math.floor(Math.random() * myArray.length);
var rs = myArray.splice(ri, 1);
document.getElementById("showSplice").innerHTML = text+=rs;
//document.getElementById("showArrayList").innerHTML = myArray;
}
}

It "always" draws 2 elements because of the i+=text. Your array is small thus the loop needs 2 iteration (of cocatinating the strings to get the number i) to go over myArray.length.
First iteration:
i = 0 => 0 < myArray.length => true
prints number
Second iteration: (say '4' get choosen)
i = i + text and text = '4' => i = "04" => "04" < myArray.length => true
prints number
Third iteration: (say '3' get choosen)
i = i + text and text = '43' => i = "0443" => "0443" < myArray.length => false
loop breaks
So there is a possibility that two elements get printed. Depending on the length of the array, there could be more.
You don't need the loop, just choose a number and print it:
function RandomDraw() {
if(myArray.length > 0) { // if there still elements in the array
var ri = Math.floor(Math.random() * myArray.length); // do your job ...
var rs = myArray.splice(ri, 1);
document.getElementById("showSplice").textContent = rs; // .textContent is better
}
else {
// print a message indicating that the array is now empty
}
}

Another solution is to shuffle the array and then, on each click, pop the element from the shuffled array.
function shuffle(array) {
return array.sort(function() { return Math.random() - 0.5; });
}
var button = document.getElementById('button');
var origin = ['1','2','3','4','5','6','7'];
var myArray = shuffle(origin);
var currentValue = null;
button.onclick = function() {
currentValue = myArray.pop();
if(!!currentValue) {
console.log(currentValue);
}
}
<button id='button'>
get element
</button>
You can shuffle the array again on each click, but I think it is not necessary whatsoever...
If you're wondering about Math.random() - 0.5:
[...] Math.random is returning a number between 0 and 1. Therefore, if you call Math.random() - 0.5 there is a 50% chance you will get a negative number and 50% chance you'll get a positive number.
If you run a for loop and add these results in an array, you will effectively get a full distribution of negative and positive numbers.
https://teamtreehouse.com/community/mathrandom05

I would do it this way:
let myArray=['1','2','3','4','5','6','7']
function RandomDraw(){
const selectedIndex = Math.floor(Math.random() * myArray.length);
const selected = myArray[selectedIndex]
myArray = myArray.slice(0, selected).concat(myArray.slice(selected + 1));
return selected;
}
Every time you call RandomDraw it will return a random number, without repeating.

The way I understand it, you want to draw every items from the array after a single click. So the loop is needed.
As others have said, there are several issues in your for loop :
that i+= text makes no sense
you are looping until i reaches the length of your array, but you are splicing that array, hence reducing its length
You could correct your for loop :
function RandomDraw() {
var length = myArray.length;
var ri = 0;
for (var i=0;i<length;i++) {
ri = Math.floor(Math.random() * myArray.length);
console.log("Random index to be drawn : " + ri);
// removing that index from the array :
myArray.splice(ri, 1);
console.log("myArray after a random draw : ", myArray);
}
}
Or, you could use a while loop :
function RandomDraw() {
var ri = 0;
while (myArray.length > 0) {
ri = Math.floor(Math.random() * myArray.length);
console.log("Random index to be drawn : " + ri);
// removing that index from the array :
myArray.splice(ri, 1);
console.log("myArray after a random draw : ", myArray);
}
}

Taking apart a Function Expression - Struggling with a Couple Lines/Parameters

So I'm looking at a piece of code that is confusing me despite reading an explanation or two:
Here's the code..
var puzzlers = [
function (a) { return 8*a - 10; },
function (a) { return (a-3) * (a-3) * (a-3); },
function (a) { return a * a + 4; },
function (a) { return a % 5; }
];
var start = 2;
var applyAndEmpty = function (input, queue) {
var length = queue.length;
for (var i = 0; i < length; i++) {
input = queue.shift()(input);
}
return input;
};
alert(applyAndEmpty(start, puzzlers));
I understand most of it but a breakdown would be great, what really boggles me is the beginning and end of this line input = queue.shift()(input); I know it's using input to store the outcome, but why? and why is there an input parameter on the end as well?
PS This line alert(applyAndEmpty(start, puzzlers)); I know calls the function then alerts it. Why do I have to call a function before I can alert/console log etc it? Is this because it isn't IIFE and so theres nothing to actually alert until the function has been called? Its quite like an 'on' button?
Sorry this is long, thanks in advance!

I've slightly edited the code in the for loop for clarity.
// This array contains 5 items, each item is a function which takes a single param and returns a number.
var puzzlers = [
function (a) { return 8*a - 10; },
function (a) { return (a-3) * (a-3) * (a-3); },
function (a) { return a * a + 4; },
function (a) { return a % 5; }
];
// The start value is 2.
var start = 2;
var applyAndEmpty = function (input, queue) {
// Get the number of items in the queue.
var length = queue.length;
// Iterate over all the items in the queue.
for (var i = 0; i < length; i++) {
// Remove the item at index 0 from the queue, the item is stored in the var.
var itemMethod = queue.shift();
// Execute the method, pass it the current value as input param. The result
// of the method will be placed back into the input variable.
input = itemMethod(input);
}
// Return the modified input value.
return input;
};
// Runs the applyAndEmpty method and shows the output in an alert.
alert(applyAndEmpty(start, puzzlers));
// The breakdown of the for loop:
// i = 0, input = 2 -> return 8 * 2 - 10 = 6
// i = 1, input = 6 -> return (6-3) * (6-3) * (6-3) = 27
// i = 2, input = 27 -> return 27 * 27 + 4 = 733
// i = 3, input = 733 -> return 733 % 5 = 3
// And thus the alert says three.
If you don't place the result of the current itemMethod back into input it means you will call each method from puzzlers with the value 2. The result of applyAndEmpty would no longer be 3 but just be 2 as the input variable is never changed. So if you don't store the result of calling the puzzler methods you might as well skip them altogether and just return the input param immediately.

It's just a way to chain the functions in the array, so that the result from the first function is passed to the second function, the result from the second function is passed to the third function, and so on...
f = [ a => 8 * a - 10,
a => (a-3) * (a-3) * (a-3),
a => a * a + 4,
a => a % 5 ]
console.log(f[3](f[2](f[1](f[0](2))))) // 3
console.log(f.pop()(f.pop()(f.pop()(f.pop()(2))))) // 3
console.log((a => a % 5)((a => a * a + 4)((a => (a-3) * (a-3) * (a-3))((a => 8*a - 10)(2))))) // 3

Uncontrolled iteration in loop

Thats my code:
var randomCoord = function(cells) {
var step = $('.workplace').innerWidth()/cells;
var xCord = (Math.floor(Math.random() * (cells+1)))*step;
var yCord = (Math.floor(Math.random() * (cells+1)))*step;
if(plants.length != 0) {
for (var i=0; i<plants.length; i++) {
if (plants[i].left != xCord && plants[i].top != yCord) {
plants.push({"top": yCord, "left": xCord});
}
}
} else {
plants.push({"top": yCord, "left": xCord});
}
};
var multiplayer = function(func, endIteration, cells) {
for (var i=0; i<endIteration; i++) {
func(cells);
};
};
multiplayer(randomCoord, 5, 10) // will iterate diferent times
Function, multiplayer have to run "randomCoords" 5 times, but it's not working. Why quantity of iteration is uncontroled? How can I fix it?

It looks like your for loop in randomCoord() is supposed to be only pushing an entry into the array if the coordinates don't already exist in the array, but that isn't how your logic works. Instead, you check each and every item in the array and if it's not equal to that item in the array, you push it and you do that for each item in the array so you end up with lots of duplicates in the array (exactly what you're trying to prevent).
So, the first time you call randomCoord, you get one item. The next time you call it, you get two items. The third time you call it you get 4 items, then 8, then 16. This is a fairly simple logic error.
If you just want to add one unique item each time you call randomCoord, then you could use logic like this:
var randomCoord = function(cells) {
var step = $('.workplace').innerWidth()/cells;
var xCord = (Math.floor(Math.random() * (cells+1)))*step;
var yCord = (Math.floor(Math.random() * (cells+1)))*step;
var found = false;
for (var i=0; i<plants.length; i++) {
if (plants[i].left == xCord && plants[i].top == yCord) {
found = true;
break;
}
}
if (!found) {
plants.push({"top": yCord, "left": xCord});
}
};
Note, you don't need the separate if (plants.length != 0) because the for loop already checks that and our new found variable handles the case where the array is initially empty.
If you happen to generate a coordinate conflict, this will add no item on that function call though the odds of generating two conflicting random values are fairly low as long as cells*step is a decent size number (the range of your random number generator). If you want to try it again in that case, then you need another loop to try again if a conflict is found.

Random Number with javascript or jquery

I am trying to make a script to pick random number between two numbers . but it picks same number sometimes. i donot want to repeat same number until array is finished .
Here is my code
$(document).ready(function () {
abc();
test = array();
function abc() {
res = randomXToY(1, 10, 0);
$('#img' + res).fadeTo(1200, 1);
//$(this).addClass('activeImg');
//});
setTimeout(function () {
removeClassImg(res)
}, 3000);
}
function removeClassImg(res) {
$('#img' + res).fadeTo(1200, 0.1);
//$('#img' + res).removeClass('activeImg');
abc();
}
function randomXToY(minVal, maxVal, floatVal) {
var randVal = minVal + (Math.random() * (maxVal - minVal));
return typeof floatVal == 'undefined' ? Math.round(randVal) : randVal.toFixed(floatVal);
}
});
Does Anybody have idea about this ...

You'll have to maintain a list of numbers that have already been generated, and check against this list. Re-generate a new number if you find a dupe.

If you do not want the random numbers repeating themselves you have to keep track of the some way.
If you have the range you are dealing with is relatively small, you can create an array with all possible results and simply randomly pick out of it.
function Randomizer(minVal, maxVal, floatVal){
var possible_results = []; // for larger arrays you can build this using a loop of course
var randomization_array = [];
var count = minVal;
var incrementor = floatVal || 1; // set the distance between possible values (if floatVal equals 0 we round to 1)
while (count <= maxVal) {
possible_results.push(count);
count += incrementor;
}
this.run = function(){
// if randomization_array is empty set posssible results into it
randomization_array = randomization_array.length ? randomization_array : $.merge(randomization_array, possible_results);
// pick a random element within the array
var rand = Math.floor(Math.random()*randomization_array.length);
// return the relevant element
return randomization_array.splice(rand,1)[0];
}
}
and in order to use it (it creates a specialized object for each possible range):
rand = new Randomizer(1,10,0);
rand.run();
note that this approach does not work well for very large ranges