12.展开运算符

/**
 *  spread operator 展开运算符
 *  更快,更便捷的操作数组
 *  
 */

//  function addNumbers(numbers){
//   return numbers.reduce((sum,number) => {
//     return sum + number;
//   },0)
//  }

//  const numbers = [1,2,3,4,5];
//  console.log(addNumbers(numbers));


//  function addNumbers(a,b,c,d,e){
//   var numbers = [a,b,c,d,e];
//   return numbers.reduce((sum,number) => {
//     return sum + number;
//   },0)
//  }
//  console.log(addNumbers(1,2,3,4,5));

//  function addNumbers(...numbers){
//   return numbers.reduce((sum,number) => {
//     return sum + number;
//   },0)
//  }
//  console.log(addNumbers(1,2,3,4,5,6,7,8));

var defaultColors = ["red","greed"];
var favoriteColors = ["orange","yellow"];

// concat
// defaultColors = defaultColors.concat(favoriteColors);
// console.log(defaultColors);

// console.log([...defaultColors,...favoriteColors]);

var fallColors = ["fire red","fall orange"];

// console.log([...fallColors,...defaultColors,...favoriteColors]);
// console.log(["blue","green",...fallColors,...defaultColors,...favoriteColors]);

// 练习
function validateShoppingList(...items){
  if(items.indexOf('milk') < 0 ){
    return ["milk",...items];
  }
  return items;
}

console.log(validateShoppingList("orange","bread","eggs"));