javascript - 匿名函数中循环内的变量范围

Question

我正在尝试在 Google map 中创建交互式标记。这是创建标记的数组:

var markers = [
    {"id":17,"ti":"33 Star Hotel","lat":3.14648,"lng":101.711,"ty":5,"lid":"3","desc":""},
    {"id":9,"ti":"Aquaria KLCC","lat":3.15392,"lng":101.713,"ty":10,"lid":"3","desc":""},
    {"id":28,"ti":"Batu Ferringhi","lat":5.47436,"lng":100.247,"ty":15,"lid":"4","desc":""},
];

如果标记位置 ID lid 等于 n，则标记将添加到 map n。

当单击标记时，我希望显示标记数组索引，但它们都显示i的最终值(markers.length)。

function map_center(n) {
    for ( var i = 0; i < markers.length; i++ ) {
        if ( markers[i].lid == n ) {
            var m = new google.maps.Marker({
                position: { lat: markers[i].lat, lng: markers[i].lng },
                map: map,
                title: markers[i].ti,
                icon: icons[markers[i].ty],
            });
            m.addListener( "click", function(){
                alert("click:" + i );
            });
            markers[i].dom = m;
        }
    }
}

不知何故，匿名函数需要一个参数来获取i当前值的副本。我在 SO 上找到了这个解决方案并且它有效，但我不喜欢以这种方式传递参数:

var m = new google.maps.Marker({
    position: { lat: markers[i].lat, lng: markers[i].lng },
    map: map,
    title: markers[i].ti,
    icon: icons[markers[i].ty],
    i: i
});
m.addListener( "click", function(){
    alert("click:" + this.i );
});

这应该如何正确完成？

Answer 1

将所有内容包裹在 iife 中

function map_center(n) {
for ( var i = 0; i < markers.length; i++ ) {
    (function(i) {
        if ( markers[i].lid == n ) {
            var m = new google.maps.Marker({
                position: { lat: markers[i].lat, lng: markers[i].lng },
                map: map,
                title: markers[i].ti,
                icon: icons[markers[i].ty],
            });
            m.addListener( "click", function(){
                alert("click:" + i );
            });
            markers[i].dom = m;
        }
    })(i)
}