使用函数设置JavaScript对象的值

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!

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);

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); vf = 100; console.log("f changed to 100"); console.log("v.total = " + v.total);