fcc 225 Profile Lookup

/** * Created by Administrator on 2017/12/8. *///初始化变量var contacts = [    {        "firstName": "Akira",        "lastName": "Laine",        "number": "0543236543",        "likes": ["Pizza", "Coding", "Brownie Points"]    },    {        "firstName": "Harry",        "lastName": "Potter",        "number": "0994372684",        "likes": ["Hogwarts", "Magic", "Hagrid"]    },    {        "firstName": "Sherlock",        "lastName": "Holmes",        "number": "0487345643",        "likes": ["Intriguing Cases", "Violin"]    },    {        "firstName": "Kristian",        "lastName": "Vos",        "number": "unknown",        "likes": ["Javascript", "Gaming", "Foxes"]    }];function lookUp(firstName, prop){  for(var i =0; i < contacts.length; i++){      if((contacts[i].firstName === firstName) && (contacts[i].hasOwnProperty([prop]) === true)){          return contacts[i][prop];      } else if((contacts[i].firstName === firstName) &&contacts[i].hasOwnProperty([prop]) === false){ // 不存在prop的时，前面的为false, 后面的也为 false那就证明不存在          return "No such property";      }  }      return "No such contact";  //以上所有的条件都不成立时就是，firsrName不存在，或是两都都不存}console.log(lookUp("Akira", "likes"));console.log((lookUp("Sherlock", "likes")));

for循环contact数组的每一个项，[ ]和.有相同的作用。contact[i].firstName就是firstName的值。Obj.hasOwnProperty(propertypeName）用于检查给定的属性在当前对象实例中是否存在，返回布尔值。