Question

var name = new Array();
var amount = new Array();
name[0]="Peter";
amount[0]="50";
name[1]="John";
amount[1]="10";
name[2]="John";
amount[2]="20";
name[3]="Peter";
amount[3]="20";
name[4]="Mary";
amount[4]="40";

I have something like the above. My question is, how can I create a function to eliminate all the duplicates and sum up the values for each person in the arrays? Below is the results I am looking for.

For example:

Peter 70
John  30
Mary  40

Answer 1

Try the following

var sum = {};
var i;
for (i = 0; i < amount.length; i++) {
  var name = name[i];
  var oldSum = sum[name];
  if (typeof oldSum === 'undefined') {
    oldSum = 0;
  }
  sum[name] = oldSum + amount[i];
}

Now the object sum will have a property for every name in name and the value of the property will be the sum of the amounts which had the that name

To print it out try the following

for (var prop in sum) {
  if (sum.hasOwnProperty(prop)) {
    console.log(prop + " " sum[prop]);
  }
}