从数组中找到最小值和最大值的高性能和最佳方法

Question

I have a array there are some prices. I want to get the min and max. I have a way but I dont know if this way is bad an inefficent. Is there a better/performant way?

Array:

sizes_and_colors: [
      {
        color: 'black',
        size: 'XS',
        amount: 3,
        price: 24.99
      },
      {
        color: 'black',
        size: 'S',
        amount: 4,
        price: 24.99
      },
      {
        color: 'blue',
        size: 'S',
        amount: 5,
        price: 24.95
      },
      {
        color: 'blue',
        size: 'XL',
        amount: 0,
        price: 24.95
      },
      {
        color: 'purple',
        size: null,
        amount: 4,
        price: 22.95
      },
      {
        color: 'beige',
        size: null,
        amount: 4,
        price: 20.99
      },
      {
        color: 'pink',
        size: 'S',
        amount: 2,
        price: 20.99
      },
      {
        color: 'green',
        size: null,
        amount: 4,
        price: 20.99
      },
      {
        color: 'silver',
        size: null,
        amount: 4,
        price: 20.99
      },
      {
        color: 'yellow',
        size: null,
        amount: 4,
        price: 20.99
      },

get lowest/highest pirce:

// get lowest price of the arr of sizes and colors
export const getLowestPrice = (sizes_and_colors: any) => {
  let arr: number[] = [];
   sizes_and_colors.map((el:any) => {
      if(el.price) {
        arr.push(el.price);
      }
   })
   return Math.min(...arr);
}

// get highest price of the arr of sizes and colors
export const getHighestPrice = (sizes_and_colors: any) => {
  let arr: number[] = [];
   sizes_and_colors.map((el:any) => {
      if(el.price) {
        arr.push(el.price);
      }
   })
   return Math.max(...arr);
}

I am very thankful for your answers and help.... ...........................................................................................

Answer 1

Just map to the price and take the max/min

// get lowest price of the arr of sizes and colors
export const getLowestPrice = (sizes_and_colors: any) => {
   return Math.min(...sizes_and_colors.map((el) => el.price));
}

// get highest price of the arr of sizes and colors
export const getHighestPrice = (sizes_and_colors: any) => {
   return Math.max(...sizes_and_colors.map((el) => el.price));
}

Answer 2

Theory:

Finding any specific element in an unsorted array is an O(n) operation, so a single loop over all array elements. You currently seem to be doing one loop to extract the numeric components of an object, and then feeding them to Math.min() or Math.max() , which will have to do another loop. So you're doing O(2n) for one value, O(4n) for both.

If you know you're gonna need both, you can just keep two variables and check for both min and max in every loop iteration.

let min = Infinity, max = -Infinity;
for(let i = 0; i < arr.length; ++i)
{
    let p = arr[i].price;
    if(p < min) min = p;
    if(p > max) max = p;
}

Certainly not idiomatic JavaScript, but this way you get both values in O(n) .

Practice:

Run tests. JavaScript engines apply all sorts of crazy optimisations, and it may very well be possible that builtins like Array.map() and Math.min() / Math.max() enjoy better optimisation than a hand-rolles JavaScript loop.

Also, beware of diminishing returns. If you expect the array to not contain at least a thousand elements, then worrying about performance on searching it is almost certainly a waste of time, and going with Samathingamajig's answer is likely preferrable for readability.

But if performance truly is critical in your case, benchmark a raw loop against the other solutions. Do a couple million iterations, run them across different browsers, etc.