Add numbers in Array using recursion and disregarding any other data type

Question

Forgive me if this is to basic or have been asked already, but I'm stuck at this problem and I feel like it must be something simple I'm not seeing.

I want to add all numbers in the array using recursion(done!) and I'm missing a statement to ignore all other types of values. For example:

var arr = [1,'a','b',2,[1],'c']
sumValues(arr) // => 4 . 

function sumValues(arr){
  if(arr.length === 0){
    return 0;
  } // if the array is empty
  if(arr.length > 0){
    if(Array.isArray(arr[0])){
      return sumValues(arr[0]);
    } // if the next element is an array
    return arr.shift() + sumValues(arr);
  }
}

Your recursive call for nested arrays uses arraySum instead of sumValues. — user1106925
– user1106925, Commented Mar 14, 2017 at 15:46
So then you're asking how to differentiate between a string and a number? — user1106925
– user1106925, Commented Mar 14, 2017 at 15:48

dana · Accepted Answer · 2017-03-14 16:48:15Z

2

You can use Number.isFinite(value) to determine whether a variable is a number other than NaN or Infinity.

Based on this test, check and conditionally add values to the summation.

function sumValues(arr){
	if (arr.length === 0){
		return 0;
	} // if the array is empty
	if (arr.length > 0) {
		if (Array.isArray(arr[0])){
			return sumValues(arr[0]);
		} // if the next element is an array

		// pop the first element off the array
		var value = arr.shift();
		// check its type and conditionally add it to the summation
		return (Number.isFinite(value) ? value : 0) + sumValues(arr);
	}
}

var arr = [1,'a','b',2,[1],'c']
console.log(sumValues(arr)); // 4

arr = [1,'3','b',2,[1,[4,3]],'c'];
console.log(sumValues(arr)); // 11 (because '3' is ignored)

edited Mar 14, 2017 at 16:48

answered Mar 14, 2017 at 15:48

dana

18.3k7 gold badges71 silver badges91 bronze badges

Sign up to request clarification or add additional context in comments.

10 Comments

nils Over a year ago

This doesn't account for NaN. Use Number(value) === value to check if it is a Number instead.

dana Over a year ago

Thanks for the tip!

Tschallacka Over a year ago

it breaks on string numbers. [1,'3','b',2,[1,[4,3]],'c'];

dana Over a year ago

Should '3' be considered a number? My take is no, but only the OP can answer for sure. I've updated my answer slightly.

dana Over a year ago

All good suggestions :) I switched to Number.isFinite but left things like that since the question was really about determining whether a value was a number.

|

Tschallacka · Accepted Answer · 2017-03-14 16:18:36Z

You can use isNaN() to test if something is Not a Number. By using the boolean inversion operator ! you can test if it's a number: !isNaN(variable)

Basically it says: if variable is Not Not A Number
A double negative is a positive, so it becomes: if variable Is a Number

function sumValues(arr){
  if(Array.isArray(arr)) {
     if(arr.length > 0) {
       // Get the first value and remove it from the array.
       var first = arr.shift();
       
       // Test if it's numeric.
       if(!isNaN(first)) {
          // If it is, parse the value, add the rest resulting array values.
          return parseInt(first) + parseInt(sumValues(arr));
       }
       // if the first item is an array, we need to iterate that one too.
       if(Array.isArray(first)) {
          return parseInt(sumValues(first)) + parseInt(sumValues(arr));
       }
       // It isn't a number, just continue with what's left of the array.
       return parseInt(sumValues(arr));
     }
     // The array is empty, return 0.
     return 0;
  }
  // It isn't an array
  else {
    // Is it an number?
    if(!isNaN(arr)) {
       // return the number
       return parseInt(arr);
    }
    // return 0, it's a dead end.
    return 0;
  }
}
var arr = [1,'a','b',2,[1],'c'];
console.log(sumValues(arr)) // => 4 .

arr = [1,'3','b',2,[1,[4,3]],'c'];
console.log(sumValues(arr)) // => 14 .

arr = 'foobar';
console.log(sumValues(arr)) // => 0 .

arr = '10';
console.log(sumValues(arr)) // => 10 .

arr = ['foobar',10,'20',[10,20,'foobar']];
console.log(sumValues(arr)) // => 60 .

score 0 · Accepted Answer · 2017-03-14 18:34:15Z

0

You're squashing an array, there is no need to create your own reduction function. Use Array#reduce to squash the array. Upon each iteration, check if the current element is a number; if it is, add it to the accumulator; if not, move on.

To make it recursive (as shown in the example below) check if the current element is an array; if it is, add the result of calling the function on the element to the accumulator.

const input = [1,'a','b',2,[1],'c'];

const sumValues = i => 
  i.reduce((m, e) => m + (e instanceof Array ? sumValues(e) : (isNaN(e) ? 0 : e)), 0);

console.log(sumValues(input));

edited Mar 14, 2017 at 18:34

answered Mar 14, 2017 at 18:29

user4639281

Collectives™ on Stack Overflow

Add numbers in Array using recursion and disregarding any other data type

3 Answers 3

10 Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

10 Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related