How to target e negative number from an array, and get the sum of all positive numbers?

问题

I am trying to figure it out how to target negative numbers in an array. I have this

function SummPositive( array ) {

}
SummPositive( [ 1, 2, 3, 4, 5, -2, 23, -1, -13, 10,-52 ] );

This is an array with negative and positive numbers.How to target all negative numbers from array, when you don't know how many negative numbers are in array?

For example, I am trying to...loop to entire array, find the positive numbers, store them in another array, and make a sum (1+2+3+4+5+10+23).

But i am noob, and i don't how to do that. If possible to do this only with native js

回答1:

Just make a condition to check if it's a positive or negative number, then define an empty array negatives and if the number is negative push it inside negatives array if positive add it to sum variable, check working example below.

function SummPositive( numbers ) {
  var negatives = [];
  var sum = 0;

  for(var i = 0; i < numbers.length; i++) {
    if(numbers[i] < 0) {
      negatives.push(numbers[i]);
    }else{
      sum += numbers[i];
    }
  }

  console.log(negatives);

  return sum;
}

var sum_result = SummPositive( [ 1, 2, 3, 4, 5, -2, 23, -1, -13, 10,-52 ] );

console.log(sum_result);

回答2:

You could filter the array only for positive numbers and then add all values.

var array = [ 1, 2, 3, 4, 5, -2, 23, -1, -13, 10, -52 ],
    positive = array.filter(function (a) { return a >= 0; }),
    sum = positive.reduce(function (a, b) { return a + b; });

console.log(sum);

Or use a single loop

var array = [ 1, 2, 3, 4, 5, -2, 23, -1, -13, 10, -52 ],
    sum = array.reduce(function (r, a) {
        return a > 0 ? r + a : r;
    }, 0);

console.log(sum);

Method used:

Array#filter:

The filter() method creates a new array with all elements that pass the test implemented by the provided function.
Array#reduce:

The reduce() method applies a function against an accumulator and each value of the array (from left-to-right) to reduce it to a single value.

回答3:

I think that you mean this:

function SummPositive( array ) {
    var sum = 0;
    for(var i = 0; i < array.length; i++) {
        if(array[i] > 0) {
            sum += array[i];
        }
    }
    return sum;
}

It will sum all the positive numbers in the array and return the sum.

回答4:

As a alternative you can use lastest features of ES6:

let arr = [1, 3, 1, -2];
let sum = arr.reduce(((r, x) => x > 0 ?  x + r: r), 0);
console.log(sum)

回答5:

This will delete take out all negative numbers and sum the remaining values in the array.

var totalN = 0;
for(var ctr = 0; ctr < summPositive.length; ctr++){
    if(summPositive[ctr] >= 0 ){totalN += summPositive[ctr];
    }
}

回答6:

You can simply filter the array to find positive

    function sumPositive(arr){
      var positiveArray = arr.filter(function(x){return x > 0});// getting positive.
      var sum = 0;  positiveArray.forEach(function(x){ sum += x;});
     return sum;
  }

来源：https://stackoverflow.com/questions/40227381/how-to-target-e-negative-number-from-an-array-and-get-the-sum-of-all-positive-n

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javascript

arrays

numbers