Set JavaScript Object value with a function

Question

Im trying to set an Object value with a function. essentially, im trying to calculate the total values in an object up to a certain point, which is the limit variable im passing to the calculateTotal function.

seems like im doing it wrong, any suggestions?

var sc = 0.75
com = 2197.63,
 user_input = 400,
 f11_total = 0;
var v = {
 "a": com,
 "b": (com * 0.06 * sc),
 "c": (com * 0.09 * sc),
 "d": (215.54 * Math.pow(sc, 2)),
 "e": (299.36 * sc),
 "f": 328.76,
 "g": ((com * 0.048) * (user_input / 400)),
 "h": (com * 0.01),
 "3.6": 0.036,
 "total": function() {
 calculateTotal(3.6);
 }
};
function calculateTotal(limit) {
 for (var k in v) {
 if (k == limit) return (f11_total * v[k]);
 f11_total += v[k];
 }
}
console.log(calculateTotal(3.6));

thanks!

• SLaks: What's the problem?
• Gerardo: "total": calculateTotal(3.6)
• Tyler Roper: This sounds like a pretty good chance to use get. I realize this question is "complete" but decided to throw an alternative in the ring anyway.

Answer 1

The value of the total member is getting set to the function you have defined, not it's return value.

As @Santi points out, we can't reference v inside calculateTotal until v has finished being declared.

An approach here could be to populate total after v has been declared like this:

var v = {
 "a": com,
 "b": (com * 0.06 * sc),
 "c": (com * 0.09 * sc),
 "d": (215.54 * Math.pow(sc, 2)),
 "e": (299.36 * sc),
 "f": 328.76,
 "g": ((com * 0.048) * (user_input / 400)),
 "h": (com * 0.01),
 "3.6": 0.036 
};
v.total = calculateTotal(3.6);

• Lookin Punk: i tried that but for some reason im getting an undefined result, what am i missing?
• Tyler Roper: @Jonathan.Brink I believe OP wants this to return 116.88649793999998, however the example above will return 0. And k == limit will always evaluate to true. It's the property before "total".
• Jonathan.Brink: @Santi thanks, I missed the return statement in there. I updated my answer
• Tyler Roper: @Jonathan.Brink I believe that v is undefined because you're referencing v inside it's own initialization.
• Lookin Punk: once k == limit is true (and i check, it returns true just once), the function is suppose to return 116.886... if i call the function from outside the object, it works fine.

Answer 2

The primary issue is that you're returning a function instead of an actual value.

---

Jonathan's answer is concise and correct, however I figured I'd supply you with a modern alternative using get.

It requires no manipulation/initialization of the object, is entirely self-contained, and will recalculate if/when the object is modified.

var sc = 0.75
com = 2197.63,
 user_input = 400;
var v = {
 "a": com,
 "b": (com * 0.06 * sc),
 "c": (com * 0.09 * sc),
 "d": (215.54 * Math.pow(sc, 2)),
 "e": (299.36 * sc),
 "f": 328.76,
 "g": ((com * 0.048) * (user_input / 400)),
 "h": (com * 0.01),
 "3.6": 0.036,
 get total() {
 var f11_total = 0;
 for (var k in this) {
 if (k == 3.6) return (f11_total * this[k]);
 f11_total += this[k];
 }
 }
}
console.log("v.total = " + v.total);
v.f = 100;
console.log("f changed to 100");
console.log("v.total = " + v.total);