Creating an array of cumulative sum in javascript

Question

This is an example of what I need to do:

var myarray = [5, 10, 3, 2];

var result1 = myarray[0];
var result2 = myarray[1] + myarray[0];
var result3 = myarray         


        

Answer 1

Returns sorted obj by key and sorted array!!!

var unsorted_obj = {
  "2016-07-01": 25,
  "2016-07-04": 55,
  "2016-07-05": 84,
  "2016-07-06": 122,
  "2016-07-03": 54,
  "2016-07-02": 43
};

var sort_obj = function(obj){
  var keys = [];
  var sorted_arr = [];
  var sorted_obj = {};

  for(var key in obj){
    if(obj.hasOwnProperty(key)){
      keys.push(key);
    }
  }

  keys.sort();

  jQuery.each(keys, function(i, key){
    sorted_obj[key] = obj[key];
    var val = obj[key];
    sorted_arr.push({
      idx: i,
      date: key,
      val: val
    })
  });

  return { sorted_obj: sorted_obj, sorted_arr: sorted_arr };

};

var sorted_obj = sort_obj(unsorted_obj).sorted_obj;
var sorted_arr = sort_obj(unsorted_obj).sorted_arr;

// sorted_arr = [{"idx":0,"date":"2016-07-01","val":25},{"idx":1,"date":"2016-07-02","val":43},{"idx":2,"date":"2016-07-03","val":54},...]
// sorted_obj = {"2016-07-01":25,"2016-07-02":43,"2016-07-03":54,...}

Answer 2

/*Checkout the explanation below */

nums = [1,2,3,4]
var runningSum = function(nums) { 
shoppingCart =[];
runningtotal =0;  
nums.forEach(EachValue => {  
runningtotal += EachValue
shoppingCart.push(runningtotal);  
});
return shoppingCart       
};

console.log(runningSum(nums));

/* define some numbers*/

nums = [1,2,3,4]

/* assign function runningSum , some numbers*/

var runningSum = function(nums) { 
shoppingCart =[]; /* Create a empty shopping cart to store the items */
runningtotal =0;  /* Start with your beginning bill of zero items in the cart */

/* remove a number from list of numbers call each one of the numbers from the array => EachValue using a pointer function*/

nums.forEach(EachValue => {  

         (runningtotal += EachValue) 

/* Now add the value to the runningtotal to represent items prices*/

shoppingCart.push(runningtotal);  

/* Use the push method to place it into the new array called shopping cart */ });

return shoppingCart

/* output the items currently in the shopping cart with only 1d prices */

};

    nums = [1,2,3,4]
    var runningSum = function(nums) { 
    shoppingCart =[];
    runningtotal =0;  
    nums.forEach(EachValue => {  
    runningtotal += EachValue
    shoppingCart.push(runningtotal);  
    });
    return shoppingCart       
    };

    console.log(runningSum(nums));

Answer 3

A couple more options with ES6 array spreading

[1, 2, 3].reduce((a, x, i) => [...a, x + (a[i-1] || 0)], []); //[1, 3, 6]

or

[3, 2, 1].reduce((a, x, i) => [...a, a.length > 0 ? x + a[i-1] : x], []); //[3, 5, 6]