What would be an elegant way to find the max value of a child object in javascript?
Example:
find the max quantity value of this object (here shown as json):
{"density":[
{"price":1.22837, "quantity":48201},
{"price":1.39837, "quantity":28201},
{"price":1.40107, "quantity":127011},
{"price":1.5174, "quantity":75221},
{"price":1.60600, "quantity":53271}
]}
thank you for any advice!
PS: just to clarify: of course i could loop through, but i thought there would be a more elegant way ...
There is no way other than looping thru, because you need to visit every child in order to see if the quantity
parameter is the new max. In other words, the complexity of the problem is O(n). If the children were ordered by quantity, it would be a different story (i.e. just get the first or last child in the list.)
something like the following...
var json = '{"density":[{"price":1.22837,"quantity":48201},{"price":1.39837,"quantity":28201},{"price":1.40107,"quantity":127011},{"price":1.5174,"quantity":75221},{"price":1.60600,"quantity":53271}]}'
var x = JSON.parse(json);
var max = 0;
x.density.forEach(function(item){
if (item.quantity > max) max = item.quantity;
});
After this runs, max is the max quantity
note you didn't give us correct json, so I tweaked it a bit.
Here is an example -- click run and look in your console http://jsfiddle.net/e3dQe/
There's the reduce
method of the Array prototype:
var arr = JSON.parse(objstring)["density"];
var max = arr.reduce(function(a, b) {
return Math.max(a, b.quantity);
}, 0);
Another solution would be something like
var max = Math.max.apply(null, arr.map(function(item){
return item["quantity"];
}));
For more "elegant" ways there are functional libraries which provide getter factory functions and more Array methods. A solution with such a library could look like
var max = arr.get("quantity").max();
which would do exactly the same as the above one, but nicer expressed.
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