Normally, we can set default value for function param:
//Here use "Hello" as default param var receive =function(message="Hello", handle){ handler(message); } receive("Come", function(message){ console.log(message + ", "+ "John"); });
What we can do is use function as a default param:
var receive =function(message="Hello", handler=function(message){ console.log(message + ", "+ "John"); }){ handler(message); } receive("Come"); //Come, John
Then we can use => to refactor the code:
var receive =function(message="Hello", handler= message => console.log(message + ", "+ "John")){ handler(message); } receive("Go"); //Go, John
It will be crazy: (do not use this, cannot be understood)
let receive = (message="Hello", handler= message => console.log(message + ", "+ "John")) => handler(message) receive(); //Hello John
[ES6] 07. Default Value for function param
原文：http://www.cnblogs.com/Answer1215/p/4109677.html