如何返回该对象数组的总数？

Question

I need to take the price and tax of these and return the total of everything. I'm learning so I apologize for the simple question.

const orders = [{"price":15,"tax":0.09},{"price":42,"tax":0.07},{"price":56,"tax":0.11},
{"price":80,"tax":0.11},{"price":69,"tax":0.06},{"price":68,"tax":0.14},
{"price":72,"tax":0.14},{"price":51,"tax":0.09},{"price":89,"tax":0.15},
{"price":48,"tax":0.13}];
// Do not edit code above.

/*
  Use a higher order method to get the sum of all the order totals after adding in the sales tax
*/

var ordersTotal  = orders.reduce(function(total, num) {
    return total + num;
    })
  ordersTotal;

Answer 1

You need to give reduce something to start with, in this example 0 is probably a good start. Then each num passed to reduce will be an object. Currently you're just adding the object like total = total + {"price":15,"tax":0.09} and that doesn't work. You need to look at each property you want to add. It's not clear if tax is a percentage or a total amount. Below we'll just add it, but it should be clear how to add as a percentage if you want.

 const orders = [{"price":15,"tax":0.09},{"price":42,"tax":0.07},{"price":56,"tax":0.11},{"price":80,"tax":0.11},{"price":69,"tax":0.06},{"price":68,"tax":0.14},{"price":72,"tax":0.14},{"price":51,"tax":0.09},{"price":89,"tax":0.15},{"price":48,"tax":0.13}]; var ordersTotal = orders.reduce(function(total, num) { return total + num.price + num.tax; // add properties }, 0) // start with 0 console.log(ordersTotal); 

Answer 2

Simply use Array.reduce() and Object destructing . And please make sure to pass 0 as the initial value to your reduce function.

 const orders = [{"price":15,"tax":0.09},{"price":42,"tax":0.07},{"price":56,"tax":0.11},{"price":80,"tax":0.11},{"price":69,"tax":0.06},{"price":68,"tax":0.14},{"price":72,"tax":0.14},{"price":51,"tax":0.09},{"price":89,"tax":0.15},{"price":48,"tax":0.13}]; const result = orders.reduce((a,{price,tax})=>a+price+tax,0); console.log(result); 

Answer 3

Make sure you start with a zero so it doesn't try to coerce the result into a string.

 const orders = [{"price":15,"tax":0.09},{"price":42,"tax":0.07},{"price":56,"tax":0.11}, {"price":80,"tax":0.11},{"price":69,"tax":0.06},{"price":68,"tax":0.14}, {"price":72,"tax":0.14},{"price":51,"tax":0.09},{"price":89,"tax":0.15}, {"price":48,"tax":0.13}]; // Do not edit code above. var ordersTotal = orders.reduce(function(total, order) { return total + order.price + order.tax; },0) console.log(ordersTotal,ordersTotal.toFixed(2))