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All.

I am currently working in JS. My question concerns objects and the 'this' keyword. Please see my code below:

function calcBMI(mass, height) {
    return (mass / (height^2))
};

var Mark = {
    firstName: 'Mark',
    lastName: 'Jones',
    height: 1.82,
    mass: 81.64,
    BMI: calcBMI(this.mass, this.height)
};

var John = {
    firstName: 'John',
    lastName: 'Rivera',
    height: 1.79,
    mass: 82.19,
    BMI: calcBMI(this.mass, this.height)
};

function displayData() {
    console.log('Mark\'s BMI: ' + Mark.BMI + ', ' + 'John\'s BMI: ' + John.BMI);

    if (Mark.BMI > John.BMI) {
    console.log('Mark\'s BMI is higher.')
    } else if (John.BMI > Mark.BMI) {
        console.log('John\'s BMI is higher.')
    } else {
        console.log('John and Mark have equal BMIs.')
    }
};

displayData();

The task is to use the 'this' keyword to calculate the Body Mass Indexes of two people - John and Mark, expressed by the 'Mark' and 'John' objects. The property of BMI for each object is calculated with the 'calcBMI' function, at the top.

I am expecting the function to be called whenever the Object.BMI is invoked.

Instead, the result is NaN. Specifically, the output is:

Mark's BMI: NaN, John's BMI: NaN John and Mark have equal BMIs.

Please help me to understand just where I have gone wrong. Thank you.

PS - This is my first StackOverflow question. If you have any feedback on how I may better ask questions, here, I would appreciate it. Also, my code at times has an ugly look. I happily take suggestions making it more legible and beautiful as well.

skyntax9000
  • 1
  • This is basically a scope related issue, which can be easily resolved by using a single constructor function like: http://jsfiddle.net/dgfkcj06/1/ – palaѕн Jul 06 '18 at 17:56
  • i like this approach very much. i did end up using the get method, but i will study your answer and try it next time i need it. thanks :) – skyntax9000 Jul 06 '18 at 18:52

0 Answers0