How to write a function that gets the sum of an array (Javascript)

Question

I have the following:

var numSum = function(set) {
  for(i = 0, i < set.length, i++) {
      var arrayValue = set[i];
      var totalValue = arrayValue + 
  }
}
numSum([1, 2, 3, 4]);

But all I get back is

Uncaught Syntax Error

. What am I doing wrong?

Answer 1

For loop need ; not ,

It should be

for(i = 0; i < set.length; i++)

Shortcode of x=x+y is x+=y .

But you are doing it in wrong format.

It should be

totalValue += arrayValue 

If you declare variable inside loop it'll create every time with the loop.

declare it outside of the loop.

Like this

var totalValue=0;
for(i = 0; i < set.length; i++) {
      var arrayValue = set[i];
      totalValue+= arrayValue ;
}

you don't need to declare extra variable to hold.

Try like this

var numSum = function(set) {
  var totalValue=0;
  for(i = 0; i < set.length; i++) {
       totalValue += set[i]; 
  }
  return totalValue;
}
numSum([1, 2, 3, 4]);

JSFIDDLE

You can do it using Array.prototype.reduce().

Try like this

var sum = [1, 2, 3, 4].reduce(function(prev, curr) { return prev + curr; });

JSFIDDLE

Answer 2

The following changes are required:

1. initialize totalValue outside the loop
2. use the increment-assignment operator correctly

It should be

var numSum = function(set) {
  var totalValue = 0;
  for(i = 0, i < set.length, i++) {
      totalValue += set[i];
  }
}
numSum([1, 2, 3, 4]);

Answer 3

You can Do it Like this.

var numSum = function(set) {
    var arrayValue = 0;
    for (i = 0; i < set.length; i++) {
        arrayValue += set[i];

    }
    return (arrayValue);
};
console.log(numSum([1, 2, 3, 4]));

So You need to change few Things in urs code

1. Structure of For Loop
2. use of Assignment operator. it should be like x+y or x+=y

few improvment

1. You can use only one variable to store sum and can return that.

Answer 4

There are typo mistakes

var numSum = function(set) {
  for(i = 0; i < set.length; i++) {  // replace ',' to ';'
      var arrayValue = set[i];
      var totalValue += arrayValue; //  += operator is short of totalValue = totalValue  + arrayValue
  }
}
numSum([1, 2, 3, 4]);

Answer 5

You got "Uncaught Syntax Error" for this line

var totalValue = arrayValue + 

this should be

totalValue += arrayValue;

Your numSum function will be like

function numSum (set) {
  var totalValue = 0;
  for(i = 0, i < set.length, i++) {
    totalValue += set[i];
  }
  return totalValue;
}
numSum([1, 2, 3, 4]);

Answer 6

Try this:
var numSum = function(set) {
                var arrayValue = 0;
                for(i = 0 ; i < set.length ; i++) {
                     arrayValue += set[i];                    
                }
                return arrayValue;
            }
            alert(numSum([1, 2, 3, 4]));