输入参数到JavaScript内联函数

Question

I'm reading this example snippet in googlemaps API.

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The below is an extract from the snippet.

getNormalizedCoord(coord, zoom) is a separately defined function.

The value of the getTileUrl attribute is assigned to the output of the inline function which takes (coord, zoom) as arguements.

var moonMapType = new google.maps.ImageMapType({

     getTileUrl: function(coord, zoom) {
            var normalizedCoord = getNormalizedCoord(coord, zoom);
            ....
            ....
     },
     ....
     ....
});

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Question: What are the values of the coord, zoom variables when they are called inside the inline function?

I don't see them assigned to anything prior to calling them.

Answer 1

It's taking the parameters from getTileUrl which belongs to the ImageMapTypeOptions object specification.

getTileUrl  
Type:  function(Point, number): string
Returns a string (URL) for given tile coordinate (x, y) and zoom level.

https://developers.google.com/maps/documentation/javascript/3.exp/reference#ImageMapTypeOptions