I am developing a javascript-based application, therein I have an array as below:
[-12.66, 268.2, 48.99, -1264.5, 20550, 91.2, 0, 0, 0, 0, 0, 0, 0, 0, 9235.5, 1500, 0, 0, 18.99, 0, 0, null, null, null, null, null, null, null, null, null, null]
now I want to do cumulative summation of below error until it returns null value, once it has started reading null value it should return null from there or should return as it is and should not do cumulative summation from there.
I have done as below using array.reduce:
let resultArray=[];
array1.reduce(function (acc, curr, index) { return resuleArray[index] = acc + curr }, 0);
// here array1 is source array.
However, this returns as below
[-12.66, 255.54, 304.53, -959.97, 19590.03, 19681.23, 19681.23, 19681.23, 19681.23, 19681.23, 19681.23, 19681.23, 19681.23, 19681.23, 28916.73, 30416.73, 30416.73, 30416.73, 30435.72, 30435.72, 30435.72, 30435.72, 30435.72, 30435.72, 30435.72, 30435.72, 30435.72, 30435.72, 30435.72, 30435.72, 30435.72];
What I would like to have is like below :
[-12.66, 255.54, 304.53, -959.97, 19590.03, 19681.23, 19681.23, 19681.23, 19681.23, 19681.23, 19681.23, 19681.23, 19681.23, 19681.23, 28916.73, 30416.73, 30416.73, 30416.73, 30435.72, 30435.72, null, null, null, null, null, null, null, null, null, null, null];
Please note that I will always have trailing values as null.
You need just to modify a little bit your code like this:
array1.reduce(function (acc, curr, index) {
return resultArray[index] = curr !== null ? acc + curr : null
}, 0);
So, check if curr is null.
const array1 = [-12.66, 268.2, 48.99, -1264.5, 20550, 91.2, 0, 0, 0, 0, 0, 0, 0, 0, 9235.5, 1500, 0, 0, 18.99, 0, 0, null, null, null, null, null, null, null, null, null, null];
let resultArray = [];
array1.reduce(function(acc, curr, index) {
const sum = acc + curr;
if (curr === null) {
resultArray[index] = null;
} else {
resultArray[index] = sum
}
return sum;
}, 0);
console.log(resultArray);This way even if you put a number after some null values it will continue with the cumulative summation
You could take a closure over the sum and add unil the value is null.
const
data = [-12.66, 268.2, 48.99, -1264.5, 20550, 91.2, 0, 0, 0, 0, 0, 0, 0, 0, 9235.5, 1500, 0, 0, 18.99, 0, 0, null, null, null, null, null, null, null, null, null, null],
result = data.map((sum => v => sum === null || v === null
? sum = null
: sum += v
)(0));
console.log(...result);