Lodash flatMap method
语法：
_.flatMap(collection, [iteratee=_.identity])
Creates a flattened array of values by running each element in collection thru iteratee and flattening the mapped results. The iteratee is invoked with three arguments: (value, index|key, collection).
参数：
collection (Array|Object) − The collection to iterate over.
[iteratee=_.identity] (Function) − The function invoked per iteration.
输出：
(Array) − Returns the new flattened array.
例子：
var _ = require('lodash');
var list = [1 , 2, 3, 4, 5];
var result = _.flatMap(list, function(n) {
return [n, n];
});
console.log(result);
Save the above program in
tester.js. Run the following command to execute this program.
命令：
输出：
[
1, 1, 2, 2, 3,
3, 4, 4, 5, 5
]
