太阳系
要求
将下面的代码复制到JavaScript文件中，然后按照注释中的说明进行操作。
var planets = [ "mercury" , "venus" , "earth" , "mars" , "jupiter" , "saturn" , "uranus" , "neptune" ] ;
/*
Use the forEach method to add the name of each planet
to a div element in your HTML with an id of "planets".
*/
var el = document . getElementById ( "planets" ) ;
// Use the map method to create a new array where the first letter of each planet
