var f = v => v; 

var f = function( v ) { 
 return v; 
} 

var f = () => 5; 

var f = function() { return 5}; 

var sum = ( a, b) => a + b; 

var sum = function( a, b) { 
 return a +b; 
} 

var sum = (a, b) => { return a+b;} 

var getFunction = id => ({id: id, anme: "Temp"}); 

const full = ({first, last}) => first +" "+ last; 

function full(person) { 
 return person.first +" "+ person.last; 
} 

[1,2,3].map(function(x){ 
 return x*x; 
}); 

[1,2,3].map(x => x*x); 

var result = values.sort(function(a, b){ 
 return a -b; 
}); 

var result = values.sort((a, b) => a-b); 

const numbers = (...nums) => nums; 
numbers(1,2,3,4,5,6,7,8,9); //[1,2,3,4,5,6,7,8,9] 
//...nums 表示的是一个数组 
const headAndTail = ( head, ...tail) => [head, tail]; 
headAndTail(1,2,3,4,5,6,7,8,9);// [1, [2,3,4,5,6,7,8,9]]