javascript - 从按对象标识符分组的列表中查找最小值/最大值

Question

我试图在一组具有相同属性的项目中找到最大值和最小值。例如，从屏幕截图来看，crop: 18157 的最大值为 1.77，最小值为 1.68

JsFiddle:https://jsfiddle.net/kf3qhsge/

var myCrops = new Object();

for(i=0;i<crops.length;i++){
    if(crops[i]==crops[i+1]){
        var c = crops[i];
        var n = values[i];
        myCrops[i] = {"crop":c,"value":n};
    }

} 

Answer 1

您可以使用 reduce

思路是

• 遍历 crops 并将其用作 op 对象的键。
• 对于 crops 的每个值，我们检查键是否已经在 op 对象中，如果它已经存在，我们根据条件更改最大值和最小值。
• 如果不是，我们将添加一个具有适当值的新键。

var crops  = [18002, 18154, 18154, 18155, 18155, 18155, 18156, 18156, 18156, 18156, 18157, 18157, 18157, 18157, 18157, 18158, 18158, 18158, 18158, 18158, 18158, 18159, 18159, 18159, 18159, 18159, 18159, 18159, 18160, 18160, 18160, 18160, 18160, 18160, 18160, 18160, 18160, 18161, 18161, 18161, 18161, 18161, 18161, 18161, 18161, 18161, 18162, 18162, 18162, 18162, 18162, 18162, 18162, 18162, 18162, 18162, 18162, 18163, 18163, 18163, 18163, 18163, 18163, 18163, 18163, 18163, 18163, 18163, 18164, 18164, 18164, 18164, 18164, 18164, 18164, 18164, 18164, 18164, 18164, 18165, 18165, 18165, 18165, 18165, 18165, 18165, 18165, 18165, 18165, 18166, 18166, 18166, 18166, 18166, 18166, 18166, 18166, 18166, 18166, 18166, 18167, 18167, 18167, 18167, 18167, 18167, 18167, 18167, 18167, 18167, 18167, 18168, 18168, 18168, 18168, 18168, 18168, 18168, 18168, 18168, 18168, 18168, 18169, 18169, 18169, 18169, 18169, 18169, 18169, 18169, 18169, 18169, 18169, 18170, 18170, 18170, 18170, 18170, 18170, 18170, 18170, 18170, 18171, 18171, 18171, 18171, 18171, 18171, 18171, 18171, 18171, 18171, 18172, 18172, 18172, 18172, 18172, 18172, 18172, 18172, 18172, 18172, 18172, 18173, 18173, 18173, 18173, 18173, 18173, 18173, 18173, 18173, 18173, 18174, 18174, 18174, 18174, 18174, 18174, 18174, 18174, 18174, 18174, 18174, 18175, 18175, 18175, 18175, 18175, 18175, 18175, 18175, 18175, 18175, 18175, 18176, 18176, 18176, 18176, 18176];
var values = [1.69, 1.65, 1.75, 1.7, 1.7, 1.78, 1.69, 1.62, 1.75, 1.74, 1.7, 1.72, 1.68, 1.77, 1.7, 1.62, 1.74, 1.69, 1.82, 1.68, 1.64, 1.66, 1.74, 1.57, 1.7, 1.7, 1.6, 1.66, 1.72, 1.47, 1.52, 1.7, 1.63, 1.67, 1.69, 1.7, 1.51, 1.49, 1.58, 1.63, 1.66, 1.68, 1.39, 1.71, 1.61, 1.62, 1.41, 1.52, 1.46, 1.41, 1.61, 1.65, 1.36, 1.59, 1.65, 1.64, 1.72, 1.52, 1.35, 1.49, 1.65, 1.32, 1.37, 1.69, 1.62, 1.63, 1.7, 1.72, 1.7, 1.3, 1.47, 1.56, 1.5, 1.67, 1.41, 1.73, 1.71, 1.67, 1.58, 1.73, 1.56, 1.66, 1.73, 1.57, 1.69, 1.58, 1.73, 1.47, 1.7, 1.8, 1.61, 1.77, 1.79, 1.63, 1.56, 1.58, 1.59, 1.84, 1.64, 1.77, 1.63, 1.7, 1.76, 1.73, 1.83, 1.63, 1.44, 1.32, 1.74, 1.46, 1.57, 1.67, 1.4, 1.64, 1.69, 1.58, 1.76, 1.69, 1.58, 1.72, 1.43, 1.7, 1.34, 1.69, 1.64, 1.6, 1.68, 1.5, 1.69, 1.5, 1.76, 1.47, 1.7, 1.63, 1.49, 1.48, 1.15, 1.59, 1.65, 1.6, 1.46, 1.43, 1.52, 1.55, 1.63, 1.41, 1.66, 1.62, 1.66, 1.66, 1.68, 1.63, 1.66, 1.59, 1.34, 1.67, 1.68, 1.46, 1.66, 1.77, 1.71, 1.71, 1.6, 1.47, 1.71, 1.75, 1.6, 1.58, 1.35, 1.72, 1.77, 1.68, 1.64, 1.71, 1.59, 1.63, 1.74, 1.39, 1.59, 1.71, 1.72, 1.25, 1.65, 1.7, 1.67, 1.71, 1.67, 1.49, 1.69, 1.36, 1.53, 1.73, 1.57, 1.58, 1.7, 1.61, 1.61, 1.7, 1.62, 1.69];

let op = crops.reduce((op,inp,index)=>{
  let min = op[inp] && op[inp].min
  let max = op[inp] && op[inp].max
  let value = values[index]
  if(op[inp]){
    op[inp].min = value < min ? value : min
    op[inp].max = value > max ? value : max
  } else {
    op[inp] = {crop:inp,min:value,max:value}
  }
  return op
},{})

console.log(op)