Utilizing my function and the Math.max method to analyze a collection of object data

If I have an array containing objects with hundreds of fields structured like the example below:

[
  {
    "designation":"419880 (2011 AH37)",
    "discovery_date":"2011-01-07T00:00:00.000",
    "h_mag":19.7,
    "moid_au":0.035,
    "q_au_1":0.84,
    "q_au_2":4.26,
    "period_yr":4.06,
    "i_deg":9.65,
    "pha":true,
    "orbit_class":"Apollo"
  }

I am attempting to find the maximum value of "h_mag" for all the data points that meet certain criteria using this function:

function filterByPHA (neowise){
  for (let i = 0; i < neowise.length; i++) {
    let neo = neowise[i];
    if (neo.pha === true) {
      console.log(`${neo.designation}: ${neo.orbit_class}`);
    }
  }
}
filterByPHA(neowise);

The function is functioning properly.

I have made an attempt with the following code:

const maxMOID = Math.max(...filterByPHA(neowise).map(function(x){
  return x.moid_au;
}));

console.log(maxMOID);

My understanding is that this code should apply Math.max to my function filterByPHA(neowise), mapping it to a new function that returns the maximum moid value from the array within filterByPHA(neowise). However, I am encountering a 'TypeError: Cannot read properties of undefined (reading 'map')'. The 'x' in this context is simply a placeholder and I'm uncertain about what needs to be placed there to resolve this issue or if this code is even functional.

javascriptarraysfunctionmethods

Answer №1

To achieve this, you can utilize the Math.max function in conjunction with spread syntax.

See below for an example code snippet:

function filterByPHA(neowise) {
  let filteredPHA = neowise.filter(neo => neo.pha === true);

  if (filteredPHA.length > 0) {
    let maxHMAG = Math.max(...filteredPHA.map(neo => neo.h_mag));
    console.log(`Maximum h_mag for PHA objects: ${maxHMAG}`);
  } else {
    console.log("No PHA objects found");
  }
}

const neowiseData = [
  {
    "designation": "419880 (2011 AH37)",
    "discovery_date": "2011-01-07T00:00:00.000",
    "h_mag": 19.7,
    "moid_au": 0.035,
    "q_au_1": 0.84,
    "q_au_2": 4.26,
    "period_yr": 4.06,
    "i_deg": 9.65,
    "pha": true,
    "orbit_class": "Apollo"
  },
  {
    "designation": "419880 (2011 AH38)",
    "discovery_date": "2011-01-07T00:00:00.000",
    "h_mag": 20.7,
    "moid_au": 0.035,
    "q_au_1": 0.84,
    "q_au_2": 4.26,
    "period_yr": 4.06,
    "i_deg": 9.65,
    "pha": true,
    "orbit_class": "Apollo"
  }
];

console.log(filterByPHA(neowiseData));

Answer №2

Give this a try in order to see if it works.

console.log(Math.max(... neowise.filter((value) => value.pha).map((value) => value.moid_au)))

When you use console.log(), it will display the output in your console.

The function Math.max() helps find the highest value within a set of numbers.

By using neowise.filter(), you can easily filter out elements from an array by providing a function that returns true or false based on certain conditions. For instance, my function was (value) => value.pha.

.map() is used to transform elements of an array into new values based on a specific function provided as its parameter.

Answer №3

It is advisable to exit your filter function as mentioned.

Avoid using Math.max() with a large amount of data as the stack may overflow when there are around 100,000 items. Additionally, creating two intermediate arrays can be costly.

Instead, I recommend utilizing Array::reduce() for filtering and finding the maximum value in a single operation:

neowise.reduce((r, item) => (item.pha && item.h_mag > r && (r = item.h_mag), r), -Infinity);

You can observe the performance variance based on different numbers of elements:

` Chrome/121
-----------------------------------------------------------------------------
> n=1 | n=10 | n=100 | n=1000
reduce 1.00x x100m 227 | 1.00x x100m 852 | 1.00x x10m 663 | 1.00x x100k 93
map 6.92x x10m 157 | 8.23x x10m 701 | 7.95x x1m 527 | 6.44x x100k 599
-----------------------------------------------------------------------------
https://github.com/silentmantra/benchmark `


const $chunk = () => [{
"designation":"419880 (2011 AH37)",
"discovery_date":"2011-01-07T00:00:00.000",
"h_mag":Math.random()*100,
"moid_au":0.035,
"q_au_1":0.84,
"q_au_2":4.26,
"period_yr":4.06,
"i_deg":9.65,
"pha":Math.random()>.4,
"orbit_class":"Apollo"
}];

const $input=[];

// @benchmark map
Math.max(...$input.filter(x => x.pha).map(x => x.h_mag));

// @benchmark reduce

$input.reduce((r, item) => (item.pha && item.h_mag > r && (r = item.h_mag), r), -Infinity);

/*@end*/eval(atob('e2xldCBlPWRvY3VtZW50LmJvZHkucXVlcnlTZWxlY3Rvcigic2NyaXB0Iik7aWYoIWUubWF0Y2hlcygiW2JlbmNobWFya10iKSl7bGV0IHQ9ZG9jdW1lbnQuY3JlYXRlRWxlbWVudCgic2NyaXB0Iik7dC5zcmM9Imh0dHBzOi8vY2RuLmpzZGVsaXZyLm5ldC9naC9zaWxlbnRtYW50cmEvYmVuY2htYXJrL2xvYWRlci5qcyIsdC5kZWZlcj0hMCxkb2N1bWVudC5oZWFkLmFwcGVuZENoaWxkKHQpfX0='));

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