javascript- How to check if an object as a specific property

Question

I have this code, used to get a number of hours from an object and multiply them by a variable.

Here is the object 'work'

var work = [
    {'day': 27, 'hours': 7.30},
    {'day': 29, 'hours': 7.30},
    {'day': 31, 'hours': 10},
    {'day': 1, 'hours': 8.30},
    {'day': 2, 'hours': 7},
    {'day': 3, 'hours': 7},
    {'day': 5, 'hours': 7.30},
    {'day': 6, 'hours': 7},
    {'day': 7, 'hours': 7.30},
    {'day': 8, 'hours': 8},
    {'day': 9, 'hours': 9.30}
]

var payPerHour = 7;

and here my function to calculate the pay

function calculatePay()
{
    var result = 0, fResult = 0;

    for(var i = 0; i < work.length; i++) {
        Object.keys(work).forEach(function (val) {
            if (work[i].hasOwnProperty('hours'))
              result = work[i][val] * payPerHour;

            fResult += result;
        });
    }

    return fResult;
}

I have used "hasOwnProperty" to check if the property "hours" exists in work. The result of the function is NaN. Why?

with he for loop i iterate over the array and then with Object.keys(work) i go over the object that is in the array. — David Dume
– David Dume, Commented Sep 9, 2016 at 16:12
yeah, i thought it would make sense doing so. thanks for the help — David Dume
– David Dume, Commented Sep 9, 2016 at 16:18
All those .30's make me wonder if your data is off a bit. Should those be .5 for half-hours? or :30 for 30 minutes, with some further translation still to do before calculation? — Scott Sauyet
– Scott Sauyet, Commented Sep 9, 2016 at 17:08

tymeJV · Accepted Answer · 2016-09-09 16:09:35Z

4

You're already iterating your array via the for loop - then you do

Object.keys(work).forEach(function(val) {

This doesn't make any sense. work is an array - not an object. Basically if you remove that line it'll work:

for(var i = 0; i < work.length; i++) {
  //Object.keys(work).forEach(function(val) {
    if(work[i].hasOwnProperty('hours'))
      result = work[i]["hours"] * payPerHour; //use the right property here

    fResult += result;
  //});
}

A simpler way may be to use Array.reduce

var totalHourPay = work.reduce(function(total, workDay) {
    if (workDay.hasOwnProperty("hours")) {
         total += workDay.hours * payPerHour;
    }

    return total;
}, 0);

answered Sep 9, 2016 at 16:09

tymeJV

105k14 gold badges165 silver badges158 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Scott Sauyet Over a year ago

Or simply work.reduce((total, workDay) => total + (workDay.hours || 0) * payPerHour, 0).

tymeJV Over a year ago

@ScottSauyet -- Ya - if the ES6 syntax is available :D

Scott Sauyet Over a year ago

Sure, the ES6 is a nice change, but also removing the hasOwnProperty check in favor of || 0 makes it more succinct, and to my eyes more readable.

user6801750 · Accepted Answer · 2016-09-09 16:22:27Z

0

You can use Javascript for..in loops like below:

function calculatePay() {
    var result = 0, fResult = 0;
    for(var index in work) {
      		if(work[index].hasOwnProperty('hours'))
			result = work[index]['hours'] * payPerHour;
			fResult += result;
    }
     return fResult;
 }

answered Sep 9, 2016 at 16:22

user6801750

2423 silver badges12 bronze badges

Comments

shakeel osmani · Accepted Answer · 2016-09-09 16:23:21Z

0

I believe this is what you wanted:

var work = [{'day': 27, 'hours': 7.30},
      {'day': 29, 'hours': 7.30},
      {'day': 31, 'hours': 10},
      {'day': 1, 'hours': 8.30},
      {'day': 2, 'hours': 7},
      {'day': 3, 'hours': 7},
      {'day': 5, 'hours': 7.30},
      {'day': 6, 'hours': 7},
      {'day': 7, 'hours': 7.30},
      {'day': 8, 'hours': 8},
      {'day': 9, 'hours': 9.30}
      ];

var payPerHour = 7;

var result = 0, fResult = 0;

function calculatePay(){

for(var i = 0; i < work.length; i++) {
   Object.keys(work).forEach(function() {

   result = work[i].hours * payPerHour;
   fResult += result;
 });

}

console.log("Final total: " +fResult);
}

calculatePay();

answered Sep 9, 2016 at 16:23

shakeel osmani

7364 silver badges17 bronze badges

Comments

score 0 · Accepted Answer · 2016-09-09 20:48:58Z

Why these complicated expressions? Try this ES6 solution:

var work = [{'day':27,'hours':7.30},{'day':29,'hours':7.30},{'day':31,'hours':10},
           {'day':1,'hours':8.30},{'day':2,'hours':7},{'day':3,'hours':7},
           {'day':5,'hours':7.30},{'day':6,'hours':7},{'day':7,'hours':7.30},
           {'day':8,'hours':8},{'day': 9, 'hours': 9.30}],
           calculatePay=(b)=>work.reduce((c,d)=>c+d.hours*b,0)

// Test
console.log( calculatePay(7) ) // Returns 600.6 and 7 is your rate per hour

// Or redefine function calculatePay this way if you need ES5 compatibility
// function calculatePay(a) {
//   return work.reduce(function(b,c) {
//     return b + c.hours * a
//   }, 0)
// }

// And if you really needs use hasOwnProperty, define it this way
// function calculatePay(a) {
//   return work.reduce(function(b,c) {
//     return b + (c.hasOwnProperty('hours') && c.hours || 0) * a
//   }, 0)
// }

// But you dont need hasOwnProperty. You are processing simple array,
// not object. And this array is full of ordinary object literals. None of
// them does not inherits anything from another object, unless you override
// Object itself.

Collectives™ on Stack Overflow

javascript- How to check if an object as a specific property

4 Answers 4

3 Comments

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

3 Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related