Where is the mistake? I want to sum every number in the array. The alert says NaN.
var numbers = [10, 42, 5, 87, 61, 34, 99];
var i = 0;
var e = 0;
while(i <= numbers.length) {
e = e + numbers[i];
i++;
}
alert(e);
6 Answers
This line is the reason:
while(i <= numbers.length) {
Arrays are 0 index so you can go from index 0 (inclusive) until numbers.length (exclusive). You are going beyond that limit, causing you to access an element that isn't defined at the given index. You must do this instead:
while(i < numbers.length) {
answered Jan 18, 2017 at 20:45
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Comments
Alternatively using the ES2015 syntax you can do it like this.
let numbers = [10, 42, 5, 87, 61, 34, 99];
let sum = numbers.reduce((a,b) => a + b);
You can read about Array.prototype.reduce(accumulator, element, callback, startingValue) here.
5 Comments
Andrew Li
But they asked what was wrong with their code... not for an alternative. Solve the problem first then offer an alternative.
Maciej Caputa
Thank you @Andrew, I will do that now.
user2330678
Its a good answer and helps future readers. Please don't drop ES syntax.
Andrew Li
@user2330678 Agreed, but solve the problem at hand first. I agree the ES6 syntax is preferred but answer the question first.
Maciej Caputa
I just emphasised it is an alternative, the other answers give a hint of what was wrong in the original solution.
Your condition is wrong, just use < insteead of <=
while(i < numbers.length)
Comments
There's a few ways you can improve this. The first is that you want to change your condition to i < numbers.length, not i <= numbers.length. As you've written it, the last number will never be counted.
Another way you can improve this is using the += notation -- there's no need to write e = e + numbers[i] when you can write e += numbers[i].
Comments
You could íterate from the end of the array with a post increment and a check for truthyness in the while condition.
Inside just add the item.
var numbers = [10, 42, 5, 87, 61, 34, 99],
i = numbers.length,
e = 0;
while (i--) {
e += numbers[i];
}
console.log(e);
Comments
The problem is in array length You are checking because array index starts with 0. In that way when doing:
i <= numbers.length
You are checking [0: 10, 1: 42, 2: 5, 3: 87, 4: 61, 5: 34, 6: 99, 7:???] because numbers length is 7. To solve it just do:
i < numbers.length
where You don't check non existing number in array.
Here is how we were thought in school:
//main code//
var numbers = [10, 42, 5, 87, 61, 34, 99];
var result = sumIntArray(numbers);
//end of main code//
function sumIntArray(array){
var result = 0;
for (var i = 0; i < array.length; i++) {
if (array[i].isInteger()) {
result += array[i];
} else {
if (i === 0) {
alert("1st object in array is not number, will skip...");
}
else if (i === 1) {
alert("2nd object in array is not number, will skip...");
}
else if (i === 2){
alert("3rd object in array is not number, will skip...");
}
else {
alert((i+1).toString() + "th object in array is not number, will skip...");
}
}
}
return result;
}
The for loop adds this i++ You make in a while loop and makes code a bit more clear.
No need for declaring i in main code :)
- Always make functions to simplify main code.
- Make function that will never make mistake even if somebody wants to break The logic.
Although don't make school break Your creativity, Your code is great! :)
[42]is an array of length1. It only has an element at index0, not at index1.