CODEWITHSUNDEEP
javascriptarraysobjectmultidimensional-array
dk_french032
dk_french032

Reputation: 648

Get the sum of all specified elements in an array of objects

I have an array of objects as folllows

[
    {"width":128.90663423245883,"height":160,"X":0,"Y":140},
    {"width":277.0938568683375,"height":263,"X":128.90663423245883,"Y":37},
    {"width":264.8267031014369,"height":261,"X":277.0938568683375,"Y":39},
    {"width":229.14003389179788,"height":60,"X":264.8267031014369,"Y":240},
    {"width":10.032771905968888,"height":177,"X":229.14003389179788,"Y":123}
]

I am looking to write a function that gets the sum of all 'width' elements in the object before the current.

Something like:

function getAllBefore(current) {
    // here i want to get the sum of the previous 4 'width' elements in the object
}
getAllBefore(obj[5]);

Upvotes: 0

Views: 822

Answers (5)

VikingCode
VikingCode

Reputation: 1052

function count(stack) {
    var totWidth = 0;
    stack.forEach(function(element) {
      totWidth = totWidth+element.width;
    });
  return totWidth;
}

working example

Upvotes: 1

Aleksandar Gajic
Aleksandar Gajic

Reputation: 1359

If you are looking for solution without knowing index of element but you want only to send object, then you will need to check all properties of current item with available items and you can do it like this:

var items = [
{"width":128.90663423245883,"height":160,"X":0,"Y":140},
{"width":277.0938568683375,"height":263,"X":128.90663423245883,"Y":37},
{"width":264.8267031014369,"height":261,"X":277.0938568683375,"Y":39},
{"width":229.14003389179788,"height":60,"X":264.8267031014369,"Y":240},
{"width":10.032771905968888,"height":177,"X":229.14003389179788,"Y":123}
];

function getAllBefore(current) {
    var sum = 0;

    for (var i = 0; i < items.length; i++) {
        var item = items[i];
        if (current.width == item.width && current.height == item.height && current.X == item.X && current.Y == item.Y)
        {
             return sum;
        }

        sum += item.width;
    }
}

getAllBefore(items[2]);

Upvotes: 1

taile
taile

Reputation: 2776

Let's use reduce in JavaScript

var arr = [
    {"width":128.90663423245883,"height":160,"X":0,"Y":140},
    {"width":277.0938568683375,"height":263,"X":128.90663423245883,"Y":37},
    {"width":264.8267031014369,"height":261,"X":277.0938568683375,"Y":39},
    {"width":229.14003389179788,"height":60,"X":264.8267031014369,"Y":240},
    {"width":10.032771905968888,"height":177,"X":229.14003389179788,"Y":123}
];

console.log(arr.reduce((acc, b) => acc + b.width, 0.0));

Upvotes: 1

Benji Lees
Benji Lees

Reputation: 815

Here is an example using a slice to first return the array with the correct length and the a reduce to return the sum

const getSum = (objNum, arr) => {
  const newArr =  arr.slice(0, objNum - 1)
  return newArr.reduce((current, next) => {
    return current + next.width;
  }, 0)
}

and in ES5

var getSum = (objNum, arr) => {
  vat newArr =  arr.slice(0, objNum - 1)
  return newArr.reduce(function(current, next) {
    return current + next.width;
  }, 0)
}

and in 1 line

const getSum = (objNum, arr) => arr.slice(0, objNum - 1).reduce((current, next) =>  current + next.width, 0)

Upvotes: 3

Gianluca Paris
Gianluca Paris

Reputation: 1429

For an easier and more reusable code pass to the method the object and the index, as follows:

function getAllBefore(obj, index){
  var sum=0;
  for(var i=0; i<index; i++){
    sum+=obj[i].width;
  }

  return sum;
}

And call it like this:

getAllBefore(obj, 5);

Upvotes: 5

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