JavaScript Objects: Why Doesn't This Work?

Question

I wrote the following code. Instead of giving me an answer, it outputs NaN. I would like the code to return the weights of John and Mark. Please explain.

'use script';

//  Declaring variables
var infoJohn;
var infoMark;
var bmiCalculator;
var higherBmi;

bmiCalculator = function (height, mass) {
    var calculatedBmi;

    calculatedBmi = mass / (height * height);
    return calculatedBmi;
};

infoJohn = {
    name: 'John',
    mass: 85,
    height: 110,
    bmi: bmiCalculator(this.height, this.mass)
};

infoMark = {
    name: 'Mark',
    mass: 120,
    height: 85,
    bmi: bmiCalculator(this.height, this.mass)
};

console.log('Mark\'s BMI: ' + infoMark.bmi, 'John\'s BMI: ' + infoJohn.bmi, 
'\n\n');

Answer 1

You need to wrap bmiCalculator call to a function because otherwise this refers to a global (window) context.

This should work:

var bmiCalculator = function(height, mass) {
  var calculatedBmi;

  calculatedBmi = mass / (height * height);
  return calculatedBmi;
};

var infoJohn = {
  name: 'John',
  mass: 85,
  height: 110,
  bmi: function() {
    return bmiCalculator(this.height, this.mass);
  }
};

var infoMark = {
  name: 'Mark',
  mass: 120,
  height: 85,
  bmi: function() {
    return bmiCalculator(this.height, this.mass);
  }
};

//higherBmi = function (h)

console.log('Mark\'s BMI: ' + infoMark.bmi(), 'John\'s BMI: ' + infoJohn.bmi(),
  '\n\n');