如何删除 javascript 侦听器中的重复函数?

How to remove duplicated function in javascript listener?

Objective

我希望去除匿名函数调用带来的重复代码。

背景

我正在做一个非常简单的项目,我使用 Google 地图 API 来显示带有两个搜索框的地图。用户在这些框中输入起始地址和结束地址,然后我在地图中显示标记。

为了实现这一点,我有两个用于侦听器的匿名函数,它们完全相同,除了一点 - 一个使用 startSearchBox,另一个使用 endSearchBox.

我试过的

这种重复的代码是不必要的,因此我尝试将搜索框作为参数传递给匿名函数,但这没有用。

我也考虑过将搜索框创建为全局变量,但我希望避免这种做法。

如何消除这段代码中的重复?

代码

function initSearchBoxes() {
    // Create the search box and link it to the UI element.
    let startInput = document.getElementById('start-input');
    let startSearchBox = new google.maps.places.SearchBox(startInput);

    let endInput = document.getElementById('end-input');
    let endSearchBox = new google.maps.places.SearchBox(endInput);

    // Bias the SearchBox results towards current map's viewport.
    map.addListener('bounds_changed', function() {
        startSearchBox.setBounds(map.getBounds());
        endSearchBox.setBounds(map.getBounds());
    });

    startSearchBox.addListener('places_changed', function() {

        deleteAllMarkers();

        let places = startSearchBox.getPlaces();
        if (places.length == 0) {
            return;
        }

        // For each place, get the icon, name and location.
        let bounds = new google.maps.LatLngBounds();
        places.forEach(function(place) {

            // // Create a marker for each place.
            let newMarker = createMarker(place.geometry.location, place.name, markerLabels.nextSymbol(), true);
            markerLib.trackMarker(newMarker);

            newMarker.setMap(map);

            if (place.geometry.viewport) {
                // Only geocodes have viewport.
                bounds.union(place.geometry.viewport);
            }
            else {
                bounds.extend(place.geometry.location);
            }
        });
        map.fitBounds(bounds);
    });

    endSearchBox.addListener('places_changed', function() {

        deleteAllMarkers();

        let places = endSearchBox.getPlaces();
        if (places.length == 0) {
            return;
        }

        // For each place, get the icon, name and location.
        let bounds = new google.maps.LatLngBounds();
        places.forEach(function(place) {

            // // Create a marker for each place.
            let newMarker = createMarker(place.geometry.location, place.name, markerLabels.nextSymbol(), true);
            markerLib.trackMarker(newMarker);

            newMarker.setMap(map);

            if (place.geometry.viewport) {
                // Only geocodes have viewport.
                bounds.union(place.geometry.viewport);
            }
            else {
                bounds.extend(place.geometry.location);
            }
        });
        map.fitBounds(bounds);
    });
}

您可以将回调函数包装在另一个 "factory" 函数中。工厂将采用一个参数(搜索框引用),然后它将 return 实际处理程序:

function makeSearchHandler(searchBox) {
    return function() {

        deleteAllMarkers();

        let places = searchBox.getPlaces();
        if (places.length == 0) {
            return;
        }

        // For each place, get the icon, name and location.
        let bounds = new google.maps.LatLngBounds();
        places.forEach(function(place) {

            // // Create a marker for each place.
            let newMarker = createMarker(place.geometry.location, place.name, markerLabels.nextSymbol(), true);
            markerLib.trackMarker(newMarker);

            newMarker.setMap(map);

            if (place.geometry.viewport) {
                // Only geocodes have viewport.
                bounds.union(place.geometry.viewport);
            }
            else {
                bounds.extend(place.geometry.location);
            }
        });
        map.fitBounds(bounds);
    };
}

该函数包含原始代码,但不是直接引用 startSearchBoxendSearchBox,而是使用传递给工厂的参数。因此,returned 函数将像您的函数一样工作,但代码只出现一次。

然后您可以使用该函数创建回调:

startSearchBox.addListener('places_changed', makeSearchHandler(startSearchBox));
endSearchBox.addListener('places_changed', makeSearchHandler(endSearchBox));