I'm trying to solve a simple algorithm where you evaluate that every number in an array is greater than the next one, so I first taught in the Every() method, but when I do a return is always false, but when I console.log() it display true!
How is this possible?
const arr = [3, 2, 1];
const returnRes = arr.every((value, index, arr) => value > arr[index + 1]);
const consoleLogRes = arr.every((value, index, arr) => console.log(value > arr[index + 1]));
console.log(returnRes);
At the third iteration. The value arr[index + 1] will be undefine. why? it because the value of arr[index + 1] will be arr(2+1) which is arr[3] and arr[3] does not exist because index start from zero not 1. what you can do is to add a check at the last iteration to prevent the undefine from happening. check the code below
const arr = [3, 2, 1];
const response = arr.every((value, index, arr) => {
if (index + 1 === arr.length) {
return true;
}
return value > arr[index + 1];
});
console.log(response);
The issue is when your value is 1 and index is 2, that is, when the every function processes the last element of your array, arr[index + 1] returns undefined and 1 > undefined evaluates to false.
To properly fix it, you should return true when index is pointing to the last element:
const arr = [3, 2, 1];
const returnRes = arr.every((value, index, arr) =>
index === arr.length - 1 || value > arr[index + 1]);
console.log(returnRes);
trueyou see is the innerconsole.log()printingtrueonce, and then theeveryterminates becauseconsole.log()returnsundefined