计算数组中是否存在重复的JavaScript对象值

Count JavaScript object value in array for duplicates

本文关键字：JavaScript 对象 数组 是否 存在 计算      更新时间：2023-09-26

你好，我是社区的新手，这是我的第一个问题。

///我有一组物体。在某个时候会有几百。

var locations = [{
    "name": "Costco",
    "city": "San Francisco",
    "state": "CA",
    "zip": "75201",
}, {
    "name": "Safeway",
    "city": "Appleton",
    "state": "WI",
    "zip": "90210",
}, {
    "name": "Foodmart",
    "city": "Orlando",
    "state": "FL",
    "zip": "90210",
}, {
    "name": "Trader Joes",
    "city": "Concord",
    "state": "CA",
    "zip": "90210",
}];

///我需要计算每个"state："，并将其值作为如下所示的变量。

var CA
/// Value would be 2
var FL
/// Value would be 1
var WI
/// Value would be 1

///请原谅，我对数组的有点生疏

使用一个简单的循环，您可以做到这一点。（这使用了ES6箭头函数语法和let。很容易被var和匿名函数语法取代，以兼容旧的浏览器）

let states = {};
locations.forEach(obj => {
    if (states[obj.state]) states[obj.state]++;
    else states[obj.state] = 1;
});

这在数组上循环，检查计数器对象中是否存在条目，如果存在，则递增计数，否则添加条目并将其设置为1。

请注意，我使用了一个对象来存储计数，而不是单个变量。通过这种方式，它不那么混乱，也更容易索引。

感谢"Sterling Archer"。。。这个问题解决了。Fiddle：http://jsfiddle.net/30bdf7h2/48/

// LIST
var locations = [{
  "name": "Costco",
  "city": "San Francisco",
  "state": "CA",
  "zip": "75201",
}, {
  "name": "Safeway",
  "city": "Appleton",
  "state": "WI",
  "zip": "90210",
}, {
  "name": "Foodmart",
  "city": "Orlando",
  "state": "FL",
  "zip": "90210",
}, {
  "name": "Trader Joes",
  "city": "Concord",
  "state": "CA",
  "zip": "90210",
}];
var states = {};
locations.forEach(obj => {
  if (states[obj.state]) states[obj.state]++;
  else states[obj.state] = 1;
});
var countForCA = states["CA"];
magic();
function magic() {
  document.getElementById("state_total").innerHTML = "CA Count: "+countForCA;
  document.getElementById("array_total").innerHTML = "Array Total: " + locations.length;
}
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