Trying to loop the arguments entered and return the arguments as the total multiplication:
let lightCode = { //Creates Object.
Multiply: function() { //Multiplys all arguments.
const total = 0;
for(const i = 0; i < arguments.length; i++) {
console.log(arguments[i]);
total *= arguments[i];
}
return total;
}
}
lightCode.Multiply(12, 16)
You have two problems, one of which is that you can not reassign a value to a constant. Second you're setting total = 0 first. By doing that you'll be multiplying everything by 0.
So in order to solve your problem you need a if conditional to check if total is 0, if is 0 you assign the property total to the argument in the loop, if not you multiply it.
let lightCode = { //Creates Object.
Multiply: function() { //Multiplys all arguments.
let total = 0;
for(let i = 0; i < arguments.length; i++) {
if(total === 0) total = parseFloat(arguments[i]);
else total *= parseFloat(arguments[i]);
}
return total;
}
}
console.log(lightCode.Multiply(12, 16));
I recommend you to read about const, let, var and when to use them. There are (at least) two mistakes in your code:
const total = 0 => since total is declared using the const identifier, it means that its value is going to be constant during your program. And what does constant mean? That it stays the same. But the line total *= arguments[i]; wants to change it, resulting into an error. Also, initializing the total with 0 makes the final results to be 0 (remember that the multiplication identity element is 1).
const i = 0 => same thing; i++ wants to increment the value of i, but you declared it as const.
Running your code and opening the console you can clearly say an error message: "Uncaught TypeError: Assignment to constant variable.".
Cheers!
let lightCode = {
Multiply: function() {
var total = 1;
for (var i = 0; i < arguments.length; i++) {
console.log(arguments[i]);
total *= arguments[i];
}
return total;
}
}
lightCode.Multiply(12, 16)
As pointed in the comments, there is more than one error in the code, first you are assigning the variables as const which is not correct in this case, the rule of thumb is to use let every time you need to reassign a variable (meaning, when you need to use the =symbol again), otherwise use const. Also as pointed in the comments you should not initialize the variable with zero, otherwise the loop will always return zero.
Here is a working snippet:
const lightCode = { //Creates Object.
Multiply: function() { //Multiplys all arguments.
let total = 1; // can not be zero, otherwise the loop will always return zero
for(let i = 0; i < arguments.length; i++) {
console.log(arguments[i]);
total *= arguments[i];
}
return total;
}
}
lightCode.Multiply(12, 16)
Notice how I am using const for the lightCode variable, because this object is never reassigned (meaning, you won't use the = to assign a new value again) and instead for total I'm using let, because is reassigned on every loop interaction.
Related
I'm writing a function to calculate investment return over period of years. However, the function seems to be only able to calculate for one year. If the totalyears is more than 1, the loop as shown below is not iterating and it returns wrong value.
const calc = (initial, monthlyContribution, totalyears, annualisedReturn) => {
let sum = initial;
for (i = 0; i < totalyears; i++) { // ISSUE: THIS NOT LOOPING WHEN totalyears > 1
let balance = sum;
let totalBalance = 0;
for (i = 0; i < 12; i++) {
totalBalance = totalBalance + balance;
balance = balance + monthlyContribution;
}
sum = balance + (totalBalance / 12) * (annualisedReturn / 100);
}
return sum;
};
console.log(calc(0, 100, 2, 10)); // This return 1255 which is wrong
You're using the same global variable for both loops. i will have the value 12 when leaving the inner loop, thus the condition of the outer loop will be false
You are using the same variable "i" in the inner loop and you are not declaring it again.
So when you start the loop with i=0, your inner loop will first make i=0 again, then it will increase until i=12, and then the same variable is used in the first loop, so it will go from 0 to 12, skipping iterations. Use "i, j,k" for nested loops.
Something like this:
for (let i = 0; i < 10; i++) {
for (let j = 0; j < 10; j++) {
}
}
Iterating through a javascript array which has some data in, and some null or not defined values also, is giving funny behaviors with a for loop, but not with a while loop. It is not returning when it should and is stuck in an infinite loop
I have investigated the outputs extensively, the condition whether the number exists in the array is never evaluated to be true, only ever false, but it sometimes enters the if statement region as if it is true. It is seemingly arbitrary.
//function called within this code
function randomArrayOfIndexes() {
var randNumbArray = new Array(4);
var indexToAssign = Math.floor(Math.random() * Math.floor(4));
randNumbArray[0] = indexToAssign;
for (i = 1; i < randNumbArray.length; i++) {
indexToAssign = Math.floor(Math.random() * Math.floor(4));
while (arrayContains(randNumbArray, indexToAssign)) {
indexToAssign = Math.floor(Math.random() * Math.floor(4));
}
randNumbArray[i] = indexToAssign;
}
return randNumbArray;
}
//this works
function arrayContains(arrayin, numberIn) {
var i = arrayin.length;
while (i--) { //takes one from i so highest index is accurate on first iteration
if (arrayin[i] === numberIn) {
return true;
}
}
return false;
}
//this doesn't... not even backwards like the above iteration
function arrayIncludes(arrayin, numberIn) {
for (i = 0; i < arrayin.length; i++) {
if (arrayin[i] === numberIn) {
return true;
}
}
return false;
}
At first each function above is passed in an array with [int value, null, null, null], and a random number; when the function returns, the next null value is filled with the random number that doesn't exist in it already, so [int value, int value, null, null]... until all values are filled... the final array is filled with unique random numbers from 0 to 3, to provide an index for a piece of data in another array... to make sure that it is only used once in the program I am writing.
I would expect it to return true if the number passed in is already in there, another random number then generated outside of the broken function, and the process repeated until a unique random number is found. When it is found, the array being passed back in will be populated at the next available index, and the process repeated. This is not happening. It is getting stuck in an infinite loop, and never returning
you are just missing a var before i:
function arrayIncludes(arrayin, numberIn) {
for (var i = 0; i < arrayin.length; i++) {
// in ^ here
if (arrayin[i] === numberIn) {
return true;
}
}
return false;
}
You may also declare it before loop, like
var i;
for (i = 0; i < arrayin.length; i++) {
...
By the way, this way of generating random numbers without duplicates is very inefficient, I suggest something like having an array of 0-3 (in your current example) or 0-n and then just randomly taking items out of it. then you don't have to loop through the whole array each time you find a new number. every time you just find a random index between 0 and the length of remaining items.
Imagine that the array length is 1000, and the last item remaining is a number like 100, how many times you have to find a random number and loop through whole array till your random number is 100?
var n = 5;
var a = new Array(n);
for(var i=0;i<n;i++) a[i] = i;
var result = new Array(n);
var i = n;
while(i)
{
var index = Math.floor(Math.random() * i);
result[--i] = a[index];
a.splice(index,1);
}
document.getElementById('a').innerHTML = result;
<div id="a"></div>
You need to declare variables in you loops with for i=0. if you don't do this the variable is global and when you use the same loop variable in nested loops one can change the other.
You are using i in both loops so when you call the for loop with:
function arrayIncludes(arrayin, numberIn) {
for (i = 0; i < arrayin.length; i++) {
// etc
}
You set i back to 0 ad iterate it — this is the same i you are using in randomArrayOfIndexes so it interferes with that loop. This is a common cause of hard-to-find bugs and is hy you should always declare loop variables.
Here's the bug in it's simplest form. Notice that the out loop only runs once because i is incremented in the inner loop causing the outloop to exit early:
for (i = 0; i < 4; i++){
console.log("out loop number: ", i)
for (i = 0; i < 4; i++){
console.log("inner_loop: ", i)
}
}
If you declare the variables for for let i =, each loop gets its own version of i both loops run independently:
for (let i = 0; i < 4; i++){
console.log("out loop number: ", i)
for (let i = 0; i < 4; i++){
console.log("inner_loop: ", i)
}
}
I am having a huge issue with a coding problem I need to make. I am being asked to run a sum of numbers inside of an array and I can't get the code to run properly.
This is my code and below are the instructions of what I am being asked to run:
function sumOfRange(numbers){
var numbers = [1,-1,1,-1,1];
var sum = 0;
for (var i = 0; i < numbers.length; i++){
sum += numbers[i];
}
return sum;
}
// Your Challenge:
// - Create a function named sumOfRange.
// - It accepts one parameter, called numbers, that
// represents an array of numbers.
//
// - In your function, sum the numbers inside the array.
// (Reminder: you'll need a variable to store the result.)
// - Return the result.
// Hint: You do not need to create a new array - you will be
// looping through the parameter, which is already coming in as
// an array.
// Someone else will be calling your function like this:
// sumOfRange([1,2,3,4,5])
// sumOfRange([-4,-5,-10,0])
I keep getting
errors saying
You returned '1'. That isn't quite right. The sum of [1,2,3,4,5] is 15.
Any help with this would greatly appreciate it.
Remove the first line of your function sumOfRange() var numbers = [1,-1,1,-1,1] because you are re-initializing the value of numbers, you need to use to array that is passed to the function when it is called.
function sumOfRange(numbers) {
var sum = 0;
for (var i = 0; i < numbers.length; i++) {
sum += numbers[i];
}
return sum;
}
console.log(sumOfRange([1,-1,1,-1,1]));
console.log(sumOfRange([1,2,3,4,5]));
console.log(sumOfRange([-4,-5,-10,0]));
var a = [1,2,3,4,5];
function sum (arr) {
return arr.reduce(function(prev, curr) {
return prev + curr;
}, 0);
}
//sum(a) -> returns 15
I am trying to learn Javascript. I've built the following code to find the average from an array of numbers. It works except the last returned value is always NaN. I cannot figure out why. If I move this piece outside of the block it seems to forget altogether what the variable sum is supposed to be equal to. Is there some kind of global-variable type equivalent I'm supposed to be using for JS?
var average = function(myarray) {
sum = 0;
for (counter = 0; counter <= myarray.length; counter++) {
sum = sum + myarray[counter];
average = sum / myarray.length;
console.log(average);
};
}
average([1, 2, 3])
Change
counter <= myarray.length
to
counter < myarray.length
because indexes start at 0.
Full example:
var average = function(myarray) {
var sum = 0;
for (var counter = 0; counter < myarray.length; counter++) {
sum += myarray[counter];
}
return sum / myarray.length;
}
console.log(average([1,2,3]));
JSBin Demo: http://jsbin.com/siyugi/1/edit
myarray[myarray.length] is undefined, which intoxicates your computation with NaN(Not A Number).
Just change it to
for(counter = 0; counter < myarray.length; counter ++) {
// ...
}
Since you are just learning you should know it is good practice to not use .length in a for loop like that. It causes the code to have to check the length of your array on each loop. And remember that .length is returning the number of elements in the array; but array index starts at 0.
for(var counter = 0, length = myarray.length; counter < length; counter++){
}
Would be the proper way to do it.
Don't use variables without declaring them with var keyword, otherwise they will become global properties.
The JavaScript Arrays are zero index based arrays. So, if the size of the array is 3, then the first element will be accessed with 0 and the last with 2. JavaScript is very forgiving, so when you access an element at an invalid index in the array, it will simply return undefined.
In the iteration, you are replacing the current function object with the average value. So, subsequent calls to average will fail, since average is not a function object any more.
It is a good practice to have a function return the computed value, instead of printing the value, so that it will not violate the Single Responsibility Principle.
In your case,
for (counter = 0; counter <= myarray.length; counter++) {
The counter runs till the last index of the array + 1. Since it returns undefined in the last iteration, JavaScript returns NaN in the arithmetic operation.
console.log(1 + undefined);
# NaN
So, you need to change the code, like this
function Average(myarray) {
var sum = 0, counter;
for (counter = 0; counter < myarray.length; counter++) {
sum = sum + myarray[counter];
}
return sum / myarray.length;
}
If you are interested, you can compute the sum with Array.prototype.forEach, like this
function Average(myarray) {
var sum = 0;
myarray.forEach(function(currentNumber) {
sum += currentNumber;
});
return sum / myarray.length;
}
Even better, you can calculate the sum with Array.prototype.reduce, like this
function Average(myarray) {
return myarray.reduce(function(sum, currentNumber) {
return sum + currentNumber;
}, 0) / myarray.length;
}
You can calculate the average of an array of numbers as follows:
var avg = c => c.reduce((a,b) => a +b) / c.length;
avg([1,2,3])
function averageCalculator (numvalues) {
for(i=0, i <= numvalues, i++>) {
var score = prompt("input the score")
result1 += score;
}
alert(result1 / 3);
}
this function is later triggered by a button with onclick="averageCalculator (2)
<input type="button" value="Click for the average" onclick="averageCalculator (2)">
any ideas why its not working? it should prompt you for 2 values and then alert you with the average. not sure whats wrong.
Your code has multiple issues. The for loop is not well formatted and you need to terminate statements with a semi-colon. Also you need to declare variables. And your loop will run numvalues+1 times which is why i removed the = in your loop. Also if you want to calculate an average you want to divide by numvalues.
function averageCalculator (numvalues) {
var result1 = 0;
for(i=0; i < numvalues; i++) {
var score = prompt("input the score");
result1 += score;
}
alert(result1 / numvalues);
}
On top of the invalid syntax you will run into a common "problem" with javascript here. The inputs are treated as strings and instead of being added they will be concatenated. Providing 2 and 2 as scores will result in 11. 2 concatenated with 2 = 22 / 2 = 11. You need to cast the value to a number explicitly before adding them together:
function averageCalculator (numvalues) {
var result1 = 0;
for(i=0; i < numvalues; i++) {
var score = prompt("input the score");
result1 += Number(score);
}
alert(result1 / numvalues);
}
Above code will correctly return 2
The syntax of your for-loop is wrong:
for(i=0, i <= numvalues, i++>) {
should be
for(i=0; i <= numvalues; i++) {
Tip: Also, it's better to use
for(var i=0; i <= numvalues; i++) {
since then i will be a local variable instead of a global one.
Try like this
for(var i=0; i <= numvalues; i++){}
An alternative solution (using a functional programming libary, like Underscore.js):
function averageCalculator(numValues) {
var numbers = _.map(_.range(numValues), function(element) {
return +prompt('input the score');
});
var result = _.reduce(numbers, function(memo, number) {
return memo + number;
}, memo);
alert(result / 3);
}
While a little bit more complicated (and less efficient), you'll get rid of loops altogether.
EDIT
The +prompt('input the score') does effectivly the same as Number(prompt('input the score')).