I want to perform an operation involving the current and the next array element.
For example, add current element with the next:
let arr = [0,1,2,3,4,5];
let newarr = arr.map((a,b) => a+b); //here, a and b are treated as the same element
expecting it to yield a new array of sums of current and next array element:
[0+1, 1+2, 2+3, 3+4, 4+5]
Is it possible to do that with map? If not, is there any other method that is suitable for manipulating multiple array elements in one operation?
here, a and b are treated as the same element
No. a is the value and b is the index. They happen to be the same in your particular data set.
Is it possible to do that with map?
Not with map itself. That will give you a new value for each value in the array, but you are starting with 6 values and ending up with 5, so you need an additional transformation.
Obviously you also need to use "the next value" instead of "the current index" too.
const arr = [0,1,2,3,4,5];
const newarr = arr.map((value, index, array) => value + array[index + 1]);
newarr.pop(); // Discard the last value (5 + undefined);
console.log(newarr);
[0, 1, 0, 0, 2] would produce [1, 1, 2]You could slice the array and map with the value and value at same index of original array.
const
array = [0, 1, 2, 3, 4, 5],
result = array.slice(1).map((v, i) => array[i] + v);
console.log(result);The second parameter in map is the index. Since map returns results for each iteration you can filter the unwanted item from the new array:
let arr = [0,1,2,3,4,5];
let newarr = arr.map((a,b) => a+arr[b+1]).filter(i => !isNaN(i));
console.log(newarr);You can use reduce for that:
const arr = [0, 1, 2, 3, 4, 5];
const out = arr.reduce((acc, el, i) => {
if (i === arr.length - 1) { // don't do anything for the last element
return acc;
}
acc.push(el + arr[i + 1]);
return acc;
}, []);
console.log(out)Using Array.prototype.slice(), Array.prototype.forEach().
const data = [0, 1, 2, 3, 4, 5],
numbers = data.slice(0, -1),
result = [];
numbers.forEach((number, index) => {
result.push(number + data[index + 1]);
});
console.log(result);.forEach() over .map() here?