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trying to divide negatives and positives in JavaScript

Very new, trying to make a function that takes out and separates all negatives/positives/zeros in an array. So far Ive been able to make an acceptable for loop but only with hard coded numbers. Dont currently know how to convert it into a function. please help.
var arr=[1,3,5,-9,-3,0];
var new_arr = [];
var new_arr2 = [];
var new_arr3=[];
for(i =0; i < arr.length; i++){
if(arr[i]>0){
new_arr.push(arr[i]);
}
else if(arr[i]<0){
new_arr2.push(arr[i]);
}
else if(arr[i]===0){
new_arr3.push(arr[i]);
}
}
console.log(new_arr3.length/arr.length);
console.log(new_arr2.length/arr.length);
console.log(new_arr.length/arr.length);

How about something like this?
function division(arr) {
var new_arr = [];
var new_arr2 = [];
var new_arr3 = [];
for (i = 0; i < arr.length; i++) {
if (arr[i] > 0) {
new_arr.push(arr[i]);
} else if (arr[i] < 0) {
new_arr2.push(arr[i]);
} else if (arr[i] === 0) {
new_arr3.push(arr[i]);
}
}
console.log(new_arr3.length / arr.length);
console.log(new_arr2.length / arr.length);
console.log(new_arr.length / arr.length);
}
division([1, 3, 5, -9, -3, 0]);
This new function takes the array as a parameter, so all you need to do is call it and pass the array.

You can try this way also, here I am considering 0 as a positive number. If you want, you can tweak the condition as per requirement.
function positive_negative(array ){
positive = array.filter(function (a) { return a >= 0; });
negative = array.filter(function (a) { return a < 0; });
return [positive,negative];
}
var array = [1,3,5,-9,-3,0];
console.log(positive_negative(array));

Having trouble getting rid of duplicates in JavaScript.

var numberArray = [1,2,3,4, 5,6,7,8,9, 9, 4];
var newArray = [];
function primeChecker(arrayCheck){
for (var i = 0; i < arrayCheck.length; i++){
if (Math.sqrt(arrayCheck[i]) % 1 === 0) {
newArray.push(arrayCheck[i]);
}
}
for (var x = 0; x < newArray.length; x++){
newArray.sort();
if (newArray[x] === newArray[x -1]){
newArray.splice(newArray[x-1]);
}
}
}
primeChecker(numberArray);
console.log(newArray);
The returned array is [ 1, 4, 4, 9 ]. The function successfully gets rid of the repeating 9s but I am still left with two 4s. Any thoughts as to why this might be? I am a JavaScript beginner and not totally familiar with the language.

Loop backwards. When you remove the item from the array the array gets shorter.

https://jsfiddle.net/2w0k5tz8/
function remove_duplicates(array_){
var ret_array = new Array();
for (var a = array_.length - 1; a >= 0; a--) {
for (var b = array_.length - 1; b >= 0; b--) {
if(array_[a] == array_[b] && a != b){
delete array_[b];
}
};
if(array_[a] != undefined)
ret_array.push(array_[a]);
};
return ret_array;
}
console.log(remove_duplicates(Array(1,1,1,2,2,2,3,3,3)));
Loop through, remove duplicates, and create a clone array place holder because the array index will not be updated.
Loop backward for better performance ( your loop wont need to keep checking the length of your array)

You do not need insert the number that already is in newArray, you can know what element is in the array with the method indexOf.
Try it in the if, and you can delete the second cicle for.
Something like this:
if (Math.sqrt(arrayCheck[i]) % 1 === 0 && newArray.indexOf(arrayCheck[i])==-1)

checking if sum of array is greater than max number and vice versa javascript

function ArrayAdditionI(arr) {
var numbers = arr();
var arraySum = "";
for (var i = 0; i < numbers.length; i++) {
arraySum = arraySum + arr[i];
};
if (numbers.max() <= arraySum) {
arr = true
}
else if (numbers.max() > arraySum) {
arr = false;
}
return arr;
}
I need to find the numbers stored in an array called arr and check if they add up to or total the greatest number or whether they do not. If so, return true. If not, return false.
I am not sure I am calling the array correctly in the beginning.
Thanks

I actually wrote a library I use just for functions like this.
http://code.google.com/p/pseudosavant/downloads/detail?name=psMathStats.min.js
You would just do this:
var arr = [1,2,3,4,5,300];
if (arr.max() > arr.sum()){
// Max is greater than sum...
}
One warning though. This library prototypes the Array object which could mess up other scripting that uses for (var i in arr) on an Array, which you shouldn't ever do. I am actually almost done with v2 of the library with a number of new functions and it no longer prototypes the Array object.
You can just grab the .max() and .sum() methods from the code, and use them without the prototyping if you want though.
maxArray = function (arr) {
return Math.max.apply(Math, arr);
}
sumArray = function (arr) {
for (var i = 0, length = arr.length, sum = 0; i < length; sum += arr[i++]);
return sum;
}

You mean something like this?
function ArrayAdditionI(arr) {
for (var i = 0, sum=0; i < arr.length; i++) {
sum += arr[i];
}
return Math.max.apply( Math, arr ) <= sum;
}

function ArrayAdditionI(input) {
var arraySum, max;
arraySum = max = input[0];
for (var i = 1; i < input.length; i++) {
arraySum += input[i];
if(input[i] > max){
max = input[i];
}
};
return arraySum >= max;
}

If the numbers are positive, the answer is guaranteed - the sum is always greater than or equal to the max. If you need to calculate it, ddlshack's code looks good.
Looking at your code, there are a number of issues. First of all, arr() should error out. Arrays aren't functions, and trying to treat them as a function does nothing. Your array is already usable when it is passed in. Additionally, you want to initialize arraySum to 0, not "". The way you are doing it, the values in the array will be coerced into strings and concatenated together, which is not what you are looking for. Finally, arrays don't implement a max() method, but Math does, and functions/methods in javascript can be applied to an array in the manner shown by ddlshack and others.

There are some syntax errors: type missmatch, wrong assign and calls to method that doesn't exists. If I'm understanding what do you want to do, this is the correct code(if changing items order is not a problem):
function ArrayAdditionI(arr) {
var ret = false;
var arraySum = 0;
for (var i = 0; i < arr.length; i++) {
arraySum += arr[i];
}
if (arr.sort()[arr.length-1] <= arraySum) {
ret = true
}
return ret;
}

how to compare two arrays of different length if you dont know the length of each one in javascript?

I am stuck in this. I got 2 arrays, I don't know the length of each one, they can be the same length or no, I don't know, but I need to create a new array with the numbers no common in just a (2, 10).
For this case:
var a = [2,4,10];
var b = [1,4];
var newArray = [];
if(a.length >= b.length ){
for(var i =0; i < a.length; i++){
for(var j =0; j < b.length; j++){
if(a[i] !=b [j]){
newArray.push(b);
}
}
}
}else{}
I don't know why my code never reach the first condition and I don't know what to do when b has more length than a.

It seems that you have a logic error in your code, if I am understanding your requirements correctly.
This code will put all elements that are in a that are not in b, into newArray.
var a = [2, 4, 10];
var b = [1, 4];
var newArray = [];
for (var i = 0; i < a.length; i++) {
// we want to know if a[i] is found in b
var match = false; // we haven't found it yet
for (var j = 0; j < b.length; j++) {
if (a[i] == b[j]) {
// we have found a[i] in b, so we can stop searching
match = true;
break;
}
// if we never find a[i] in b, the for loop will simply end,
// and match will remain false
}
// add a[i] to newArray only if we didn't find a match.
if (!match) {
newArray.push(a[i]);
}
}
To clarify, if
a = [2, 4, 10];
b = [4, 3, 11, 12];
then newArray will be [2,10]

Try this
var a = [2,4,10];
var b = [1,4];
var nonCommonArray = [];
for(var i=0;i<a.length;i++){
if(!eleContainsInArray(b,a[i])){
nonCommonArray.push(a[i]);
}
}
function eleContainsInArray(arr,element){
if(arr != null && arr.length >0){
for(var i=0;i<arr.length;i++){
if(arr[i] == element)
return true;
}
}
return false;
}

I found this solution just using the filter() and include() methods, a very and short easy one.
The filter() method creates a new array with all elements that pass the test implemented by the provided function.
The includes() method determines whether an array includes a certain value among its entries, returning true or false as appropriate.
function compareArrays(a, b) {
return a.filter(e => b.includes(e));
}

Random number generator without dupes in Javascript?

I need help with writing some code that will create a random number from an array of 12 numbers and print it 9 times without dupes. This has been tough for me to accomplish. Any ideas?

var nums = [1,2,3,4,5,6,7,8,9,10,11,12];
var gen_nums = [];
function in_array(array, el) {
for(var i = 0 ; i < array.length; i++)
if(array[i] == el) return true;
return false;
}
function get_rand(array) {
var rand = array[Math.floor(Math.random()*array.length)];
if(!in_array(gen_nums, rand)) {
gen_nums.push(rand);
return rand;
}
return get_rand(array);
}
for(var i = 0; i < 9; i++) {
console.log(get_rand(nums));
}

The most effective and efficient way to do this is to shuffle your numbers then print the first nine of them. Use a good shuffle algorithm.What Thilo suggested will give you poor results. See here.
Edit
Here's a brief Knuth Shuffle algorithm example:
void shuffle(vector<int> nums)
{
for (int i = nums.size()-1; i >= 0; i--)
{
// this line is really shorthand, but gets the point across, I hope.
swap(nums[i],nums[rand()%i]);
}
}

Try this once:
//Here o is the array;
var testArr = [6, 7, 12, 15, 17, 20, 21];
shuffle = function(o){ //v1.0
for(var j, x, i = o.length; i; j = parseInt(Math.random() * i), x = o[--i], o[i] = o[j], o[j] = x);
return o;
};
shuffle(testArr);

This is relatively simple to do, the theory behind it is creating another array which keeps track of which elements of the array you have used.
var tempArray = new Array(12),i,r;
for (i=0;i<9;i++)
{
r = Math.floor(Math.random()*12); // Get a random index
if (tempArray[r] === undefined) // If the index hasn't been used yet
{
document.write(numberArray[r]); // Display it
tempArray[r] = true; // Flag it as have been used
}
else // Otherwise
{
i--; // Try again
}
}
Other methods include shuffling the array, removing used elements from the array, or moving used elements to the end of the array.

If I understand you correctly, you want to shuffle your array.
Loop a couple of times (length of array should do), and in every iteration, get two random array indexes and swap the two elements there. (Update: if you are really serious about this, this may not be the best algorithm).
You can then print the first nine array elements, which will be in random order and not repeat.

Here is a generic way of getting random numbers between min and max without duplicates:
function inArray(arr, el) {
for(var i = 0 ; i < arr.length; i++)
if(arr[i] == el) return true;
return false;
}
function getRandomIntNoDuplicates(min, max, DuplicateArr) {
var RandomInt = Math.floor(Math.random() * (max - min + 1)) + min;
if (DuplicateArr.length > (max-min) ) return false; // break endless recursion
if(!inArray(DuplicateArr, RandomInt)) {
DuplicateArr.push(RandomInt);
return RandomInt;
}
return getRandomIntNoDuplicates(min, max, DuplicateArr); //recurse
}
call with:
var duplicates =[];
for (var i = 1; i <= 6 ; i++) {
console.log(getRandomIntNoDuplicates(1,10,duplicates));
}

const nums = [1,2,3,4,5,6,7,8,9,10,11,12];
for(var i = 1 ; i < 10; i++){
result = nums[Math.floor(Math.random()*nums.length)];
const index = nums.indexOf(result);
nums.splice(index, 1);
console.log(i+' - '+result);
}