We Keep Coding

JavaScript change value every time a function is called

I'm making a blackjacks or 21 game, and I cannot figure out why my function value won't change, basically, this function gives you a random number, and what I want it to do is, give it a new number each time this function is called, and not the same one up to three times. (depending on the users choice.) If someone is able to solve this, I would be much appreciated, thanks.
function cardNumber(a, b) {
var cardTotal = a + b;
alert(`Your card numbers are ${a} and ${b}!`);
return cardTotal;
}
var cardRange = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
var cardOne = cardRange[Math.floor(Math.random() * cardRange.length)];
var cardTwo = cardRange[Math.floor(Math.random() * cardRange.length)];
var cardSum = cardNumber(cardOne, cardTwo);
//want to give new number each time this function is called below
function moreCards(a, b) {
alert(`Your extra card is ${a}!`);
var cardTotal = a + b;
return cardTotal;
}
extraCard = cardRange[Math.floor(Math.random() * cardRange.length)];
var i;
for (i = 0; i < 3;) {
var input = prompt(`Which makes your card total ${cardSum}. Would you like to draw another card? (Type in 1 for yes, 0 for no, or select cancel to return to home.)`);
if (input === null) {
window.location.replace("http://stackoverflow.com"); //placeholder link
//take this back to home.html ^^^
i += 3;
}
//Random number doesn't change
else if (input === "1") {
i++;
cardSum = moreCards(extraCard, cardSum);
}
//Random number doesn't change
else if (input === "0") {
i += 3;
}
else {
alert("Wrong input, enter 1 or 0 on your keyboard!");
}
}

When you set a variable, it only gets set once - even if you are setting it to the return of a function. To fix your code, you need to make your variable ExtraCard into a function, such as
function extraCard() {
let newCard = cardRange[Math.floor(Math.random() * cardRange.length)]
return newCard
}
and then change where you call the variable to call it as a function, like so:
else if (input === "1") {
i++;
cardSum = moreCards(extraCard(), cardSum);
}

Count amount of time a number appears in an Array

So I have a dice rolling function. I want to roll 2 dice 20 times, each time I roll, I want to add those numbers, and then I want to see how many times the sum appears, and put that number into an array.
function Dice() {
this.roll = function() {
var randomValue = Math.ceil(Math.random() * 6);
this.side = randomValue;
return this.side;
}
}
var dice1 = new Dice();
var dice2 = new Dice();
function getAmount() {
var finalArray = [];
function diceSum() {
var sum = dice1.roll() + dice2.roll();
return sum;
}
var trackSum = [];
for (var i = 1; i <= 20; i++) {
trackSum.push(diceSum());
}
var reduced = trackSum.reduce(function(acc, sum, i, arr) {
return acc.i += sum;
}, {});
return reduced;
}
so I get trackSum which has 20 numbers in an array which, each number is the sum of the 2 dice rolled. If sum = 2 and it appears 5 times, sum = 4, appears 2 times, sum = 3, appears 1 time, final array should look like
[5, 2, 1]
So far I tried a reduce method, filter, and forEach. I just can't figure out how to compare the numbers to see how many times it's appearing. Any help would be appreciated. Thanks!

Use an object whose keys are the sums, and values are the number of times the sum appears. Loop through trackSum and increment the value of the corresponding element.
var freq = {};
trackSum.forEach(function(sum) {
freq[sum] = freq[sum] ? freq[sum] + 1 : 1;
}
console.log(freq);

Apologies for answering my own question, but after some googling, I figured it out. So don't pay attention to the reduce method I have in my original post. This is what I did instead:
var countedSum = trackSum.reduce(function(emptyObj, sum, i, arr){
if (sum in emptyObj){
emptyObj[sum]++
} else {
emptyObj[sum] = 1
}
return emptyObj;
}, {});
This returns an object, with the sum value as the key, and the amount of times it happens as the value.
Then I learned a new method that grabs the values and puts it in an array.
Object.values(countedSum)
That solves it!
Thanks #Barmar for your help!

Most frequently occuring number (mode) in a list - want to get only the highest value

I'm trying to get whatever number is the most frequently occuring number in an array, so for an array containing 1,2,10,5,1 the result should be 1. The code I wrote returns me the frequency for each number, so 1 occurs twice, 2 occurs once, 10 occurs once etc. Any suggestions how I can fix my result?
function mode(arr) {
var uniqNum = {};
var numCounter = function(num, counter) {
if(!uniqNum.hasOwnProperty(num)) {
uniqNum[num] = 1;
} else {
uniqNum[num] ++;
}
};
arr.forEach(numCounter);
return uniqNum;
}

I've kept your code unchanged and added some extra statements. Here is the demo: http://codepen.io/PiotrBerebecki/pen/rrdxRo
function mode(arr) {
var uniqNum = {};
var numCounter = function(num, counter) {
if(!uniqNum.hasOwnProperty(num)) {
uniqNum[num] = 1;
} else {
uniqNum[num] ++;
}
};
arr.forEach(numCounter);
return Object.keys(uniqNum)
.sort((a,b) => uniqNum[b] - uniqNum[a]) // sort by frequency
.filter((val,ind,array) => uniqNum[array[0]] == uniqNum[val]) // leave only most frequent
.map(val => Number(val)); // convert text to number
}
console.log( JSON.stringify(mode([3,3,2,4,4])) ) // [3,4]
console.log( JSON.stringify(mode([2,4,3,3])) ) // [3]

I think it could be done only with a little modification to your forEach loop and the assistance of another auxiliary data structure:
function mode(arr) {
var freq = [], uniqNum = {}, i;
arr.forEach(function (num) {
uniqNum[num] = i = (uniqNum[num] || 0) + 1;
freq[i] = (freq[i] || []).concat(num);
});
return freq[freq.length - 1];
}
console.log(mode([1, 2, 3, 4, 5, 1, 2, 3, 4, 5, 6, 6, 7, 1, 6]));
With only one iteration over all the elements of the array we can gather enough information to print out the result:
uniqNum is the set you created to gather info about the element's frequency.
freq will be an array which last element will contain an array with the elements of higher frequency.
Fiddle. Hope it helps.

First we want to make an array where we count the number of occurrences of a certain value up to that point.
Then we use the reduce function to return an array of values read from the original array for the indexes whose values have the current max appearances. We redefine max and empty the final output array of modes (if new max is established) as we go along. We want this to be a collection in case there is a tie for maximum appearances.
Additional advantage of the below is that it doesn't require sort which is more expensive o(nlog n) and keeps the time complexity down to just linear. I also wanted to keep the functions used down to only two (map and reduce) as it is all that is need in this case.
edit: fixed a major bug uniqNum[e] += 1 instead of uniqNum[e] + 1 which went unnoticed as my initial case array was still returning expected result. Also made the syntax more concise in favor of more comments.
var arr = [1,2,10,5,1,5,2,2,5,3,3];
//global max to keep track of which value has most appearances.
var max = -1;
var uniqNum = {};
var modeArray = arr.map(function(e) {
//create array that counts appearances of the value up to that point starting from beginning of the input arr array.
if(!uniqNum.hasOwnProperty(e)) {
uniqNum[e] = 1;
return 1;
} else {
return uniqNum[e] += 1;
}
//reduce the above appearance count array into an array that only contains values of the modes
}).reduce(function (modes, e1, i) {
//if max gets beaten then redefine the mode array to only include the new max appearance value.
if(e1 > max){
//redefining max
max = e1;
//returning only the new max element
return [arr[i]];
//if its a tie we still want to include the current value but we don't want to empty the array.
}else if(e1 == max){
//append onto the modes array the co-max value
return[...modes, arr[i]];
}
return modes;
},[]);
alert(modeArray);
Here is a test you can run of my solution against #acontell. In my browser (Chrome with V8) my solution was around three-four times faster for arrays with large number of repeating values and even bigger advantage with distributions with lower number of repeating values. #acontell 's is a cleaner looking solution for sure, but definitely not faster in execution.
var arr = [];
for(var i=0; i < 100000; i++){
arr.push(Math.floor(Math.random() * (100 - 1)) + 1);
}
console.time("test");
test();
function test(){
var max = -1;
var uniqNum = {};
var modeArray = arr.map(function(e) {
//create array that counts appearances of the value up to that point starting from beginning of the input arr array.
if(!uniqNum.hasOwnProperty(e)) {
uniqNum[e] = 1;
return 1;
} else {
return uniqNum[e] += 1;
}
//reduce the above appearance count array into an array that only contains values of the modes
}).reduce(function (modes, e1, i) {
//if max gets beaten then redefine the mode array to only include the new max appearance value.
if(e1 > max){
//redefining max
max = e1;
//returning only the new max element
return [arr[i]];
//if its a tie we still want to include the current value but we don't want to empty the array.
}else if(e1 == max){
//append onto the modes array the co-max value
modes.push(arr[i])
return modes;
}
return modes;
},[]);
}
console.timeEnd("test");
console.time("test1");
test1();
function test1 () {
var freq = [],
uniqNum = {},
i;
arr.forEach(function(num) {
uniqNum[num] = i = (uniqNum[num] || 0) + 1;
freq[i] = (freq[i] || []).concat(num);
});
return freq[freq.length - 1];
}
console.timeEnd("test1");

I've tried as an exercise to solve this with native js functions.
var arr = [1,2,10,5,1];
// groupBy number
var x = arr.reduce(
function(ac, cur){
ac[cur]?(ac[cur] = ac[cur] + 1):ac[cur] = 1;
return ac;
}, {}
);
// sort in order of frequencies
var res = Object.keys(x).sort(
function(a,b){ return x[a] < x[b]}
);
res[0] has the most frequent element

Set a range of numbers as a variable (Javascript)

Let's say I want a variable to contain numbers from 1 to 100.
I could do it like this:
var numbers = [1,2,3,4,...,98,99,100]
But it would take a bunch of time to write all those numbers down.
Is there any way to set a range to that variable? Something like:
var numbers = [from 1, to 100]
This might sound like a really nooby question but haven't been able to figure it out myself. Thanks in advance.

Store the minimum and maximum range in an object:
var a = {
from: 0,
to: 100
};

In addition to this answer, here are some ways to do it:
for loop:
var numbers = []
for (var i = 1; i <= 100; i++) {
numbers.push(i)
}
Array.prototype.fill + Array.prototype.map
var numbers = Array(100).fill().map(function(v, i) { return i + 1; })
Or, if you are allowed to use arrow functions:
var numbers = Array(100).fill().map((v, i) => i + 1)
Or, if you are allowed to use the spread operator:
var numbers = [...Array(100)].map((v, i) => i + 1)
However, note that using the for loop is the fastest.

You can easily create your own, and store only the limits:
function Range(begin, end) {
this.low = begin;
this.hi = end;
this.has = function(n) {
return this.low <= n <= this.hi;
}
}
// code example
var range = new Range(1,100);
var num = 5;
if (range.has(num)) {
alert("Number in range");
}

Supported in all modern browsers including IE9+.
var numbers = Array.apply(null,Array(100)).map(function(e,i){return i+1;});

For what it's worth, #MaxZoom had answer that worked for my situation. However, I did need to modify the return statement to evaluate with && comparison. Otherwise appeared to return true for any number.
function Range(begin, end) {
this.low = begin;
this.hi = end;
this.has = function(n) {
//return this.low <= n <= this.hi;
return ( n >= this.low && n <= this.hi );
};
}
// code example
var alertRange = new Range(0,100);
var warnRange = new Range(101, 200);
var num = 1000;
if (alertRange.has(num)) {
alert("Number in ALERT range");
//Add Alert Class
}
else if (warnRange.has(num)) {
alert("Number in WARN range");
//Add Warn Class
}
else{
alert("Number in GOOD range")
//Default Class
}

Python
# There can be two ways to generate a range in python
# 1)
a = [*range(5)]
print(a)
#[0, 1, 2, 3, 4]
# 2)
a = [*range(5,10)]
print(a)
#[5, 6, 7, 8, 9]
Javascript
// Similar pattern in Javascript can be achieved by
let a;
// 1)
a = [...Array(5).keys()]
console.log(a) //[0, 1, 2, 3, 4]
// 2)
a = [...Array(5).keys()].map(value => value + 5);
console.log(a) //[5,6,7,8,9]

JavaScript function not working for 0 value in array

This function is meant to find the highest variable in a list of variables, which have five id letters, and one number. It works fine with all the other slots, 2, 3, 4, 5, 6, 7, 8, 9, 10, but not 1. I need another set of eyes here.
The getVer function takes the number from the id; so ImpHt1 with getVer would be 1, while getShtNm gets ImpHt.
function find_max_feat(array_input,ShtNm) {
if (String(array_input[0]).length == 1) {
var max = 0;
}
else {
var max = getVer(array_input[0]);
}
var maxver = 0
var len = array_input.length;
for (var i = 0; i < len; i++) {
if (String(array_input[i]).length > 1) {
if (getShtNm(String(array_input[i])) == ShtNm) {
if (getVer(String(array_input[i])) > maxver) {
var max = array_input[i];
var maxver = getVer(String(array_input[i]));
}
}
}
}
return max;
}
0,DmnHt1_0,AltFm1_,0,0,0,0,0,0,0
An example of the array, which is why getVer is needed.
This is for a sheet generator, to be clear, but I've been working on the entire thing for at least a few days now, maybe even a week or weeks of on and off work.
The array above is generated any time a feat is selected, and the find_max_feat array is used to find the highest version in a group; it operates off of an infinite loop since nothing else I did could get it to work the way I wanted it to.
function checkFeats() {
updateFeatsel();
t=setTimeout("checkFeats()",1000);
}
function updateFeatsel() {
curselarray = new Array();
var selinc = 1;
while (selinc <= 10) {
var selincar = selinc - 1;
var selid = document.getElementById(String('ftlst' + selinc));
if (getVer(selid.options[selid.selectedIndex].title)) {
curselarray[selincar] = selid.options[selid.selectedIndex].title;
}
else {
curselarray[selincar] = 0;
}
selinc++;
}
document.getElementById('debug1').innerHTML = curselarray.valueOf();
featSelch('hlthm','ImpHt',healthom);
featSelch('strdmgm','ImpPd',Strpdom);
featSelch('strwhtm','ImpLi',Strwhtom);
featSelch('strsltm','EnhIt',StrSltom);
featSelch('endsurm','ImpEn',EndSurom);
featSelch('endsokm','ImpDf',EndSokom);
featSelch('intelmpm','ImpMg',Intelmom);
featSelch('willsokm','ImpMs',Willsokom);
featSelch('luckrllm','ImpLu',Lukrllom);
featSelch('luckpntm','EnhLu',Lukpntom);
featSelch('hlthbn','DmnHt',0);
featSelch('strbn','SupSt',0);
featSelch('luckbn','DmnLu',0);
featSelch('endbn','Armor',0)
document.getElementById('debug2').innerHTML = find_max_feat(curselarray,'DmnHt');
updateAmounts();
}
function featSelch(sid,fshtnm,defval) {
return document.getElementById(sid).innerHTML = getFeatvalue(fshtnm,defval);
}

That is because you are initialising max using getVer(array_input[0]) instead of array_input[0]. If the first item is the highest and has the version number zero, the initial value is used.
Change this:
var max = getVer(array_input[0]);
into:
var max = array_input[0];