CODEWITHSUNDEEP
javascriptfor-loopsumrange
joyfulchute
joyfulchute

Reputation: 89

How should I fix my for loop code for summing a range?

function needToAdd(start, end) {
   for(var i = start; i <= end; i++) {
    start += i;
}
return start
};

console.log(needToAdd(1, 10));
// 56

Hey guys, I just want to find out how I can sum the ranges using a for loop in javascript. What I have here works, but it gives me 56, instead of 55. What should I change in start += i to make it so that it will give me the sum of (1 + 2 + 3... + 10) instead of ( 1 + 1 + 2 + 3 + 4.... + 10)?

Upvotes: 0

Views: 56

Answers (2)

user2575725
user2575725

Reputation:

Problem is in loop you initialized i = start in the beginning and you stored the result as start += i. Hence your actual result is expected + start.

Solution 1: Use temp variable for result and return temp.

var sumInRange = function(a, b) {
  var i = t = b;
  while (a <= --i) t += i;
  return t;
};

alert(sumInRange(1, 5));
alert(sumInRange(1, 10));

Solution 2: Without temp variable

var sumInRange = function(a, b) {
  if (a === b) return a;
  return b + sumInRange(a, b - 1);
};

alert(sumInRange(1, 5));
alert(sumInRange(1, 10));

Upvotes: 0

Nikhil Aggarwal
Nikhil Aggarwal

Reputation: 28455

You need to update your code to following

function needToAdd(start, end) {
   for(var i = start+1; i <= end; i++) {
    start += i;
}
return start
}

Note: Let us say your start and end is 1. So, in this case, your loop would have executed once and have added 1 to start and would have updated it to 2. Hence, you have to execute your loop from 1 next to start.

Upvotes: 1

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