如果对象具有特定值，如何显示数组中的对象？

Question

我正在根据对象值在地图上绘制城市。

我需要能够根据它们的值隐藏或显示这些图。

到目前为止，我有以下功能，它将打开或关闭所有城市，以及一个记录城市值 <= 30 的功能。

var mapData = {
    'cities': [{"name":"Москва", "latitude":55.752, "longitude":37.615, "value":"10", "color": am4core.color("#ff0000")},
    {"name":"Старая Ладога", "latitude":60.0016, "longitude":32.2926, "value":"20", "color":chart.colors.getIndex(1)},
    {"name":"Великий Новгород", "latitude":58.33, "longitude":31.16, "value":"30", "color":chart.colors.getIndex(1)},
    {"name":"Белозерск", "latitude":60.02, "longitude":37.46, "value":"40", "color":chart.colors.getIndex(2)},
    {"name":"Изборск", "latitude":57.7082, "longitude":27.8609, "value":"50", "color":chart.colors.getIndex(3)}
]};

var imageSeries = chart.series.push(new am4maps.MapImageSeries());
    imageSeries.data = mapData.cities;
    imageSeries.dataFields.value = "value";

var imageTemplate = imageSeries.mapImages.template;
    imageTemplate.propertyFields.latitude = "latitude";
    imageTemplate.propertyFields.longitude = "longitude";
    imageTemplate.nonScaling = true

var circle = imageTemplate.createChild(am4core.Circle);
    circle.fillOpacity = 0.7;
    circle.propertyFields.fill = "color";
    circle.tooltipText = "{name}: [bold]{value}[/]";

imageSeries.heatRules.push({
    "target": circle,
    "property": "radius",
    "min": 4,
    "max": 4,
    "dataField": "value"
})




function toggleCities() {
    var series = imageSeries;
        if (series.isHiding || series.isHidden) {
        series.show();
    }
    else {
        series.hide();
    }
}

我不确定我需要更改什么才能指定只绘制值 <= 30 的城市。

Answer 1

Array.prototype.filter 将是您想要的：

const filteredData = mapData.cities.filter(d => parseInt(d.value) <= 30);

filter returns 初始数组中元素的数组，return true 从函数传递给 filter().

在你的例子中，我认为在 function toggleCities() 你会想要：

imageSeries.data = filteredData;

当您希望 <= 30 应用时，然后

imageSeries.data = mapData.cities;

当你不

如果对象具有特定值，如何显示数组中的对象？

How to display objects within an array if they have a certain value?

javascript

amcharts

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