Develop Reference

Can't get stable result with copying random values from array to an object

So I'm in process of creating a bot for a tournament and I got stuck on the part where I want to split players in pairs for play-off-style tournament. I just want to take 2 random players, get them from an array and write it as a value to a key as a round id for an object. Also I should not use those players again in the pair, so need to delete them or smth.
Here's the code:
var users = inc.funcs.getDatabase() //Getting a raw array of users (using my func that's basically a simplified fs.readFileSync func)
var tournamentPairs = new Object() //Object initialization
var id = 1
for (var i = 0; i < 16; i = i + 2) {
var first = Math.floor(Math.random() * (users.length + 1)) //Randomizing 2 indexes
var second = Math.floor(Math.random() * (users.length + 1))
var player1 = client.users.get(users[first]) //Getting the players by id
var player2 = client.users.get(users[second])
tournamentPairs[id++] = [player1.id, player2.id] //Writing to the object
users.splice(first, 1) //Deleting user's indexes from the array to not use them anymore.
users.splice(second, 1)
}
console.log(tournamentPairs)
It works perfectly on the outside, but has a bad habit of duplicating users and I once could have a gamergod98 vs gamergod98 for example. I tried console.log this crap but it often get an error when trying to console.log player2 because it's undefined for some reason. If I try to print users[second] I get undefined though it never happened for the first player. So I tried different ways to prevent situations like this: first == second. Long story short it didn't help much.
I have 9 days 'till tournament starts, any ideas on how to improve this code?

You are getting undefined because you are going out of bounds of your users list. For a list of length the last element is list[length-1], but you are generating random numbers up to length.
To fix duplicate users, remove the first selected user from the list before selecting the second one (or for a less destructive approach, mark already selected users).
var id = 1
for (var i = 0; i < 16; i = i + 2) {
var first = Math.floor(Math.random() * users.length)
var player1 = client.users.get(users[first])
users.splice(first, 1)
var second = Math.floor(Math.random() * users.length)
var player2 = client.users.get(users[second])
users.splice(second, 1)
tournamentPairs[id++] = [player1.id, player2.id]
}

Create a collection of used indexes and then if first or second are in used indexes then continue
var usedIndices = [] ;
if (usedIndices.indexOf(first) >= 0 ||
usedIndices.indexOf(second) >= 0) {
continue;
} else {
usedIndices.push(first);
usedIndices.push(second);
}
Put the usedIndices variable before for loop and the if else block inside loop after second

How to search max and min values over a json object that gets data from inputs using just javascript?

as you may see over the link (https://jsfiddle.net/andresmcio/vLp84acv/) is a simple form that stores data as:
var _newStudent = {
"code": code,
"names": names,
"grade": grades,
};
I'm having trouble getting the highest and lowest grade with their respective buttons as it is showing the last entry as either maximum and minimum value.
Would be glad if anyone could help, keeping in mind that it should be displayed as it is (With the alerts) and only using javascript, not jquery or any other.
Thanks beforehand.

It looks like you might have two problems in your functions. 1.) You are resetting the variables used to track the information with each iteration. 2.) You are only comparing each student to the same student, during each iteration. Thus, I think something like the below would provide what you are looking for.
function hghGrade(json) {
if (json.length > 1) {
var text = "";
var maxGrade = 0;
var thisGrade = 0;
for (var i = 0; i < json.length; i++) {
thisGrade = parseFloat(json[i].grade);
if (maxGrade < thisGrade)) {
maxGrade = thisGrade;
test = json[i].names + " ID code " + json[i].code + " with grade " + json[i].grade;
}
}
alert("The best grade is from: " + text);
} else {
alert("Please register at least two students");
}
}

Populate a prompt with elements of an array and number them off

(Stack Overflow doesn't have a tag for 'prompt' so I have used alert as I am guessing it is similar enough to attract the right answerers.)
Hello,
I am currently making a JavaScript-based game for an assignment at university. I am usually pretty good with problem solving but have been stumped by this issue.
To explain, I have an array which names the possible armour slots the player can pick. In any order these can be picked, and each time the choice gets pushed to a second array which handles what has already been picked (and in what order) and that item gets spliced from the original array. There is a while loop which runs through until all 3 have been picked.
var armourSlotToPick = ["Head", "Chest", "Legs"],
armourSlotPicked = [],
armourLoop = 1,
indexArmour = 0;
function numInArray() {
indexArmour++;
return (indexArmour + ". " + armourSlotToPick[indexArmour - 1] + "\n");
}
function armour() {
while (armourLoop < 4) {
var armourPick = prompt("Pick an armour slot to generate an item for:\n" + armourSlotToPick.forEach(numInArray));
if (armourPick == 1) {
armourSlotPicked.push(armourSlotToPick[0]);
armourSlotToPick.splice(0,1);
} else if (armourPick == 2) {
armourSlotPicked.push(armourSlotToPick[1]);
armourSlotToPick.splice(1,1);
} else if (armourPick == 3) {
armourSlotPicked.push(armourSlotToPick[2]);
armourSlotToPick.splice(2,1);
} else {
alert("Invalid choice, you suck");
break;
}
armourLoop++;
}
}
I know it probably wouldn't be possible to do the whole return in numInArray() to the prompt, but it shows some working.
Now the problem: I got it working so that each item in the array was numbered (var armourSlotToPick = ["1. Head", "2. Chest", "3. Legs"],) but as you could see, if the player chose 2, then the next time it would show "1. Head (new line) 3. Legs" and when the player chooses 3, a problem would occur, as they were really meant to choose 2. How is it possible to number the items in the array, in a prompt?
I'm possibly over thinking this but I have suffered for a few hours now.
I thank you in advance for any insight you may have,
Daniel.
EDIT: Solved.
Below is the end result, a slight variation from the edited answer from Jonathan Brooks.
var armourSlotToPick = [null, "Head", "Chest", "Legs"]
var armourSlotPicked = [null];
var armourLoop = 1;
function armour() {
while (armourLoop < 4) {
var message = "Pick an armour slot to generate an item for:\n";
for (var i = 0; i < armourSlotToPick.length; i++) {
if (armourSlotToPick[i] !== null) {
message += "" + i + ". " + armourSlotToPick[i] + "\n";
}
}
var armourPick = prompt(message);
if (armourPick > armourSlotToPick.length-1 || armourPick < 1) {
alert("Invalid choice, you suck");
} else {
var insert = armourSlotToPick.splice(armourPick, 1);
armourSlotPicked.push(insert);
}
armourLoop++;
}
armourSlotPicked.splice(0,1);
}
armour();
alert(armourSlotPicked.join("\n"));
I thank all that have contributed to this discussion and the end result, and I hope this is a good example for future problems people may have similar to this.

Check out my fiddle, I think I have a working solution.
What you really want to be using are Object Literals with your own indexing (starting from 1) - if it were me, I would create my own way to iterate over this custom indexing by adding a method to the Object's prototype, but I digress.
You're overcomplicating your code by using a while loop, and that large bulk of if statements is unnecessary: instead, all you need is some basic validation on the input and then you can just trust whatever input passes this validation. That is demonstrated here:
if ( armourPick > armourSlotToPick.length || armourPick < 1 ) {
alert("Invalid choice, you suck");
}
else {
armourSlotPicked.push( armourSlotToPick[armourPick-1] )
alert (armourSlotPicked[armourSlotPicked.length-1].value);
}
Read my code carefully, and you should get a better understanding of how to deal with certain issues.
EDIT:
As per your request, I think I have a solution that suits your needs. Basically all you have to do to have the arrays "start" at an index of 1 is to fill the zeroth element with a null value, like so:
var armourSlotToPick = [null, "Head", "Chest", "Legs"]
var armourSlotPicked = [null];
You just have to remember to take this null object into account in your code, for example:
if (armourSlotToPick[i] !== null) {
message += "" + i + "\n";
}
The indices will update automatically. See this updated fiddle for more details.

use structures / objects as content in the array, instead of just values.
the basic concept:
armourSlotPicked.push({ "key": 1, "value":armourSlotToPick[1]})
alert("value: " + armourSlotPicked[0].value)
alert("key: " + armourSlotPicked[0].key)
edit: responding to comments can take some space.
IMHO a prompt is the completely wrong tool for this, since most browsers would ask the user permission to prevent multiple popups, and since a promt can only return 1 piece of information, you can only ask for 1 thing per popup. Instead you ought to use a div element, with checkboxes for each information..
That being said it can easily be used in a promt.
The prompt is just a built in function, that takes a string as an argument (which is shown as text in the popup) and returns a string with the users input.
what does the magic for you is in fact this:
array.foreach(): The forEach() method executes a provided function once per array element.
in your case that means it calls a function that returns a string for each element in the array, and concatenates the strings.
in the old days you would have written this:
var messageText= "Pick an armour slot to generate an item for:\n"
for(var i = 1; i < armourSlotToPick.length; i++){
messageText += i + ". " + armourSlotToPick[i- 1] + "\n";
}
var armourPick = prompt(messageText);
but in this modern age, you define a printing function, and use it to generate the loop:
function numInArray() {
indexArmour++;
return (indexArmour + ". " + armourSlotToPick[indexArmour - 1] + "\n");
}
//more code before we get to where the function is used....
indexArmour = 0;
var messageText = "Pick an armour slot to generate an item for:\n" + armourSlotToPick.forEach(numInArray);
var armourPick = prompt(messageText);
or in a single line as in your code:
indexArmour = 0; //you forgot this - otherwise the list will only be complete once?
var armourPick = prompt("Pick an armour slot to generate an item for:\n" + armourSlotToPick.forEach(numInArray));
It produces the same output, because it does the same thing, its just written very differently!
If the array holds "object literals" instead of simply values, as I suggest, the old fashioned code would look something like this:
function contains(a, value) {
try{
for (var i = 0; i < a.length; i++) {
if (a[i].value == value) {
return true;
}
}
}
catch(err) {
// do nothing
};
return false;
}
and later..
for(var j = 0; j < 4; j++){
for(var i = 0; i < Math.min(armourSlotToPick.length); i++){
if( contains(armourSlotPicked, armourSlotToPick[i- 1]) )
continue;
var messageText = "Generate an item for armour in slot: " + i + "\n"
messageText += armourSlotToPick[i- 1] + "\n";
}
var armourPick = prompt(messageText);
if (armourPick > 0 && armourPick < armourSlotToPick.length) {
armourSlotPicked.push({"key":j, "value":armourSlotToPick[armourPick]);
}
...
}
//now we have an array that holds information about when what was picked..
or something along those lines.. this is bt.w completely untested, it's just for illustration

You want to use the array index to number your items. Since your numbers are one-based and the index is zero-based, you will need to convert between the two when outputting and interpreting the response.
This approach will also allow you to eliminate all but two of the cases in your if-else statement.

Result of FOR-loop if there is no related item

in a Podio calculation_field A I sum up the numbers of each related item (from another app) which contain "searchstring_1" in a text_field, in calculation_field B all related items which contain "searchstring_2"
No problem with the following code - IF there exists a related item. But if there exists no related item the "1" (= "nothing found"?) is displayed as "result". I tried several things, but can't find a solution for a calculation like: IF there is no related item then result = 0 (or "" or null), else let run the for-loop. Has anybody a tip what I can do?
Thanks,
Rainer
var str = all of text_field;
var num = all of number_fields;
var total = 0;
for(var i = 0; i < num.length ; i++) {
if (str[i].indexOf("searchstring_1") === 0) {
total += num[i];
}
}

The calculation field always returns the last used value if you don't explicitly specify the return value. Maybe in your case the last value of i, str[i].indexOf("searchstring_1") would return -1, I think...
To make sure that the value of totalis returned, simply add
total;
at the end of your calculation field value.
Enjoy,
Michael / Hamburg

JavaScript using isNaN to validate returns NaN

I have some code here that will make validations of whether or not the input from a text box is NOT an empty string and isNaN. When i do these validations on amounts entered, i would like it to add them up.. however when a user does not enter anything in one or more amount fields the program should just add entered fields. But instead i get NaN showing in the total field.
link to full code: http://jsfiddle.net/KxNqQ/
var $ = function (id) {
return document.getElementById(id);
}
var calculateBills = function () {
var myErrorFlag = "N";
for (i = 1; i <= 4; i++) {
AmountNumber = 'amount' + i;
AmountValue = $(AmountNumber).value;
if (AmountValue != "" && isNaN(AmountValue)) {
$(AmountNumber).style.color = "red";
myErrorFlag = "Y";
} else {
$(AmountNumber).style.color = "black";
myErrorFlag = "N";
}
}
if (myErrorFlag != "Y") {
var Amount = 0;
for (i = 1; i <= 4; i++) {
Amount += parseInt($('amount' + i).value,10);
}
$('total').value = Amount;
}
}
var clearFields = function () {
for (i = 1; i <= 4; i++) {
itemName = 'item' + i;
$(itemName).value = "";
}
for (i = 1; i <= 4; i++) {
amountName = 'amount' + i;
$(amountName).value = "";
}
$('total').value = "";
}
window.onload = function () {
$("clearfields").onclick = clearFields;
$("addbills").onclick = calculateBills;
}

I think you've got your requirements a little bit confused, or at the very least I was confused by them. So in order to answer your question, I'm going to rephrase the requirements so I understand them better. This is a useful exercise that I try to do when I'm not 100% sure of the requirements; if I can't get the requirements right, what's to say I'll get the code right?
So the requirements – as I understand them – are:
Given each amount input
When the input has a value
And that value is a number
Then add the value to the total
And make the input color black
But if the input does not have a value
Or that value is not a number
Then make the input color red
Going through your code, I can see a number of problems with it. First, I noticed that both AmountNumber and AmountValue are global variables, because they were not declared local with the var keyword. So before fixing our code, let's change that. Let's also change the variable names to something that more accurately describe what they are, hopefully making the code easier to understand:
var input = $('amount' + i);
var value = input.value;
Now, note that I chose to store the element in the input variable. This is so we don't have to look it up multiple times within the loop. Looking things up in the DOM can be expensive so we'll want to keep it to a minimum. There are other was to look up elements as well, such as getElementsByClassName, querySelector and querySelectorAll; those are left as an exercise for the reader to research and evaluate.
Next, in each iteration of the loop, you check that AmountValue is not a string and simultaneously is not a number:
if (AmountValue != "" && isNaN(AmountValue)) {
This will be true so long as AmountValue is truthy (which is the case for non-empty strings) and so long as isNaN thinks it's a number (which is the case for strings that contain numbers.) It really is rather confusing; if I understand your code correctly this clause is there to check for invalid input and if it is true should mark the input field red and set a flag. I.e. this is the but clause in the aforementioned requirements.
Let's rewrite this to be the when clause instead, we'll take care of the but later. Before we do that, let's look at the myErrorFlag. It's used – I think – to see whether all input is well formed and in that case, add it all up. Well, validation and summation can be done in one fell swoop, so let's get rid of the flag and sum the values while validating them. So we replace myErrorFlag with a total variable:
var total = 0;
Now, let's get back to our clause. The requirements say:
When the input has a value
And that value is a number
Then add the value to the total
In code, that should look something like this:
if (value && !isNaN(value)) {
total += parseInt(value, 10);
input.style.color = 'black';
}
There are a couple of things going on here. For one, the if statement has been turned on its head a bit from what it was. It first checks to see that value is truthy, then that it is a number. The second check can be a bit tricky to read, because it is essentially a double negation; in english it reads "is not not a number", i.e. "is a number". I'll leave it as an exercise for the reader to figure out whether there's a more easily understood way of writing this check.
Now what about the but clause in our requirements?
But if the input does not have a value
Or that value is not a number
Then make the input color red
Well, it's essentially the inverse of our previous statement, so let's simply add an else clause:
else {
input.style.color = 'red';
}
Because the requirements doesn't mention the total variable in this clause, it is simply ignored and doesn't show up in the end result.
Adding it all up (no pun intended) the code – with comments – looks like this:
var calculateBills = function () {
var total = 0;
for (i = 1; i <= 4; i++) {
// Given each amount input
var input = $('amount' + i);
var value = input.value;
if (value && !isNaN(value)) {
// When the input has a value
// And that value is a number
// Then add the value to the total
total += parseInt(value, 10);
// And make the input color black
input.style.color = 'black';
} else {
// But if the input does not have a value
// Or that value is not a number
// Then make the input color red
input.style.color = 'red';
}
}
$('total').value = total;
};
There are more things that could be learned from this to make for better code. For instance, this code will break if the number of inputs change, or if their id names change. This is because they are selected specifically by their IDs and as such, if those change then this code will no longer function.
Another potential issue is that we're setting inline styles on the inputs as we loop over them. This means that in order to keep this code up to date with the styling of the site, it'll have to change. Generally, mixing styling and functionality like this is not a good idea and should be avoided. One way of doing so is to use class names instead, and toggle these on and off. Incidentally, this could also help the previous problem I mentioned.
There are other problems as well, but we'll leave those for another day. Hope this helps!

Try this
var calculateBills = function () {
var Amount = 0;
for (i = 1; i <= 4; i++) {
var AmountElement = $('amount' + i),
AmountValue = AmountElement.value;
if (AmountValue != "" && !isNaN(AmountValue)) {
AmountElement.style.color = "red";
Amount += parseInt(AmountValue,10);
} else {
AmountElement.style.color = "";
}
}
$('total').value = Amount;
};
Demo
Anyway, instead of using elements with id like id="amount1", id="amount2", id="amount3", etc., you could use classes (e.g class="amount") and get them with .getElementsByClassName