freeCodeCamp中一些有趣的方法

1. 过滤对象(找到数组中(collection)与之(source)匹配对象,过滤掉数组中(collection)不匹配对象)

 function where(collection, source) {
   var arr = [];
   var keys = Object.keys(source);
   arr = collection.filter(function(item){
     for (var i = 0; i < keys.length; i++) {
       if ( !item.hasOwnProperty(keys[i]) || item[keys[i]] !== source[keys[i]]) {
         return false;
       }
     }
     return true;
   });
   // What's in a name?

   return arr;
 }

 where([{ first: "Romeo", last: "Montague" }, { first: "Mercutio", last: null }, { first: "Tybalt", last: "Capulet" }], { last: "Capulet" });