我正在寻找一个非常快速,干净和有效的方法来获得以下JSON切片中的最大“y”值:

[
  {
    "x": "8/11/2009",
    "y": 0.026572007
  },
  {
    "x": "8/12/2009",
    "y": 0.025057454
  },
  {
    "x": "8/13/2009",
    "y": 0.024530916
  },
  {
    "x": "8/14/2009",
    "y": 0.031004457
  }
]

for循环是唯一的方法吗?我很喜欢用Math.max。


当前回答

在对象数组中找到属性“Y”值最大的对象

一种方法是使用Array reduce..

const max = data.reduce(function(prev, current) {
    return (prev.y > current.y) ? prev : current
}) //returns object

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/Reduce http://caniuse.com/#search=reduce (IE9及以上版本)

如果你不需要支持IE(只支持Edge),或者可以使用预编译器,比如Babel,你可以使用更简洁的语法。

const max = data.reduce((prev, current) => (prev.y > current.y) ? prev : current)

其他回答

又快又脏:

Object.defineProperty (Array.prototype“分钟”, { 价值:函数(f) { F = F || (v => v); 返回。Reduce ((a, b) => (f(a) < f(b)) ?A: b); } }); Object.defineProperty (Array.prototype‘麦克斯’, { 价值:函数(f) { F = F || (v => v); 返回。Reduce ((a, b) => (f(a) > f(b)) ?A: b); } }); console.log ([1, 2, 3] .max ()); console.log([1, 2, 3]。Max (x => x*(4-x))); console.log ([1, 2, 3] .min ()); console.log([1, 2, 3]。Min (x => x*(4-x)));

const getMaxFromListByField = (list, field) => { 
    return list[list.map(it => it[field]).indexOf(Math.max(...list.map(it => it[field])))] 
}
// Here is very simple way to go:

// Your DataSet.

let numberArray = [
  {
    "x": "8/11/2009",
    "y": 0.026572007
  },
  {
    "x": "8/12/2009",
    "y": 0.025057454
  },
  {
    "x": "8/13/2009",
    "y": 0.024530916
  },
  {
    "x": "8/14/2009",
    "y": 0.031004457
  }
]

// 1. First create Array, containing all the value of Y
let result = numberArray.map((y) => y)
console.log(result) // >> [0.026572007,0.025057454,0.024530916,0.031004457]

// 2.
let maxValue = Math.max.apply(null, result)
console.log(maxValue) // >> 0.031004457

谢谢你在这里找到的答案,我希望它能对别人有用。 这个typescript函数可以被调用来搜索数组对象字段中可能存在的最大值:

function getHighestField(objArray: any[], fieldName: string) {
  return Number(
    Math.max.apply(
      Math,
      objArray?.map(o => o[fieldName] || 0),
    ) || 0,
  );
}

以这些值为例:

const scoreBoard = [
  { name: 'player1', score: 4 },
  { name: 'player2', score: 9 },
  { name: 'player3', score: 7 }
]

你可以这样调用这个函数:

const myHighestVariable = `This is the highest: ${getHighestField(scoreBoard, "score")}`;

结果会是这样的:

console.log(myHighestVariable);

这是最高的:9

注意null和空以及属性不在数组和空数组中

if ((value && value.length > 0)) {
  var maxObj = (value && value.length > 0) value.reduce(function (prev, current) {
    return ((parseInt(prev["y"]) || 0) > (parseInt(current["y"]) || 0)) ? prev : current
  })
}
{
  // else logic here
}