JavaScript:返回对象的属性

Question

我正在从freeCodeCamp进行一项名为"Profile Lookup"的挑战.我的问题似乎是我无法返回对象中属性的值.我使用点符号,但也尝试使用括号表示法.

目标是创建一个循环遍历对象数组的函数contacts,以查找给定firstName是否在所述数组中以及该对象是否包含给定对象prop.

如果同时firstName和prop存在,我们必须返回属性的值.

如果firstName找到但是prop没有,那么我们返回"没有这样的财产".

如果firstName未找到,我们将返回"无此联系".

这是我的代码:

function lookUpProfile(firstName, prop){
// Only change code below this line
    for(var i = 0; i<contacts.length; i++){
      if(contacts[i].firstName == firstName){
        if(contacts[i].hasOwnProperty(prop))
          return contacts.prop; 
        else 
          return "No such property"; 
      }
      else
        return "No such contact"; 
    }

// Only change code above this line
}

这是它应该循环的对象数组:

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"]
    }
]; 

编辑:return contacts[i].prop当我改为括号表示法然后回到点表示法时,我必须放弃[i] .即使我重新申请它,我也遇到了同样的问题.这是更新的功能:

function lookUpProfile(firstName, prop){
// Only change code below this line
    for(var i = 0; i<contacts.length; i++){
      if(contacts[i].firstName == firstName){
        if(contacts[i].hasOwnProperty(prop))
          return contacts[i].prop; 
        else 
          return "No such property"; 
      }
      else
        return "No such contact"; 
    }

// Only change code above this line
}

Answer 1

您必须将变量的值作为键返回

return contact[i][prop]; 

通过执行contacts[i].prop您返回名为的属性prop:contact[i]['prop']

完成功能

function lookUpProfile(firstName, prop){
// Only change code below this line
    for(var i = 0; i<contacts.length; i++){
      if(contacts[i].firstName == firstName){
        if(contacts[i].hasOwnProperty(prop))
          return contacts[i][prop]; 
        else 
          return "No such property"; 
      }
      else
        return "No such contact"; 
    }

// Only change code above this line
}

此外,您将在第一次迭代时返回每个案例.即使名称稍后在数组上也是如此.我们试试吧

function lookUpProfile(firstName, prop) {   
    // Try to find the right contact
    for(var i = 0; i<contacts.length; i++) {
      // Name is found
      if(contacts[i].firstName == firstName){ 
        // Return prop if exist, or error message
        if(contacts[i].hasOwnProperty(prop))
          return contacts[i][prop]; 
        else 
          return "No such property"; 
      } 
    }
    // No one with this name is found, return error
    return "No such contact";
}

我的方式(没有测试)

function lookUpProfile(firstName, prop) {   
    let contact = null
    // Try to find the right contact
    contacts.forEach(c => {
      if (!contact && c && c.firstName && c.firstName == firstname) {
        contact = c
      }
    })

    if (!contact)
      return "No such contact";
    return contact.hasOwnProperty(prop) ? contact[prop] : "No such property"
}