How to add a value in array of JSON objects on javascript?

Question

I have an array json object called payment

[ { billed : "100", owed: "50" }, { billed : "200", owed: "100" }] 

I want to sum up "billed" field and net answer should be 300. I tried the following:

let paidPaymentCents = 0; for (let payment in payments) { paidPaymentCents += payments[payment].billed; } 

Is there any better way using reduce : https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/reduce

Answer 1

JavaScript's reduce() would be the method for this. Once the JSON is parsed and you have an array or objects:

let testAry = [{ billed : "100", owed: "50" }, { billed : "200", owed: "100" }], amt = testAry // 1. isolate and parse .map(item => parseFloat(item.billed)) // 2. add up all billed .reduce((a, b) => a + b, 0); console.log(amt) 

Depending on the consistency of the data, you might want to use Number instead of parseFloat. More here: parseFloat vs Number

You can make it smaller (thanks @Devon):

 .reduce((acc, curr) => acc + parseFloat(curr.billed), 0) 

Answer 2

You could do this very easily using Array.prototype.reduce. Within the reduce, you can treat each element.billed as a number instance by wrapping it with Number. You would start with 0 as your accumulator and add each element.billed to get the total. Here is an example:

const data = [{ billed: "100", owed: "50" }, { billed: "200", owed: "100" }]; const total = data.reduce((runningTotal, element) => { runningTotal += Number(element.billed); return runningTotal; }, 0); console.log(`Total billed amount is ${total}`);

Answer 3

Each of the payment object in the loop has the structure { billed : "100", owed: "50" }

So you can do

let payments = [ { billed : "100", owed: "50" }, { billed : "200", owed: "100" }] let paidPaymentCents = 0; for (var i = 0;i < payments.length; i++) { paidPaymentCents += Number(payments[i].billed); } 

And you will have the paidPaymentCents will have the total.