if-else 在 for 循环中不起作用 - Javascript

Question

我有一个包含一些属性的数组“联系人”。我的函数使用 for 检查每个联系人的 firstName 属性是否与我的函数的 name 参数匹配，如果匹配，则检查此类联系人是否具有与 prop 参数匹配的属性（前一个 if 中的 if）。两个“if”都有对应的“else”：“no such property”、“not such contact”。

代码其实很简单：

var contacts = [
  {
    "firstName": "Akira",
    "lastName": "Laine",
    "number": "0543236543",
    "likes": ["Pizza", "Coding", "Brownie Points"]
  },
  {
    "firstName": "Harry",
    "lastName": "Potter",
    "number": "0994372684",
    "likes": ["Hogwarts", "Magic", "Hagrid"]
  },
  {
    "firstName": "Kristian",
    "lastName": "Vos",
    "number": "unknown",
    "likes": ["JavaScript", "Gaming", "Foxes"]
  }
];


function lookUpProfile(name, prop) {

  for (var i = 0; i < contacts.length; i++) {

    if (contacts[i].firstName === name) {

      if (contacts[i].hasOwnProperty(prop)) {
        return contacts[i][prop];
      }
      else {
        return "No such property";
      }
    }
    else {
      return "No such contact";}
  }  
}

console.log(lookUpProfile("Harry", "likes"));

以下几行完美运行：

console.log(lookUpProfile("Akira", "likes"));
console.log(lookUpProfile("Akira", "lala"));

现在，如果我把其余元素的任何其他 firsNames 放在一起：

console.log(lookUpProfile("Harry", "likes"));
console.log(lookUpProfile("Kristian", "likes"));

它返回“没有这样的联系”....：/

Answer 1

那是因为您在第一次循环迭代中返回 No such contact。将它放在循环之后的函数底部作为一个包罗万象的内容。

var contacts=[{"firstName":"Akira","lastName":"Laine","number":"0543236543","likes":["Pizza","Coding","Brownie Points"]},{"firstName":"Harry","lastName":"Potter","number":"0994372684","likes":["Hogwarts","Magic","Hagrid"]},{"firstName":"Kristian","lastName":"Vos","number":"unknown","likes":["JavaScript","Gaming","Foxes"]}]

function lookUpProfile(name, prop) {

  for (var i = 0; i < contacts.length; i++) {

    if (contacts[i].firstName === name) {

      if (contacts[i].hasOwnProperty(prop)) {
        return contacts[i][prop];
      } else {
        return "No such property";
      }
    }
  }
  return "No such contact";
}

console.log(lookUpProfile("Harry", "likes"));
console.log(lookUpProfile("Kristian", "likes"));
console.log(lookUpProfile("Made Up Person", "likes"));
console.log(lookUpProfile("Akira", "Made Up Property"));

Answer 2

在您当前的代码中，如果数组的第一个元素与当前传递的名称不匹配，则进入 else 块并返回“No such contact”（最终只检查第一个元素）

你从 for 循环中的 else 块错误地返回，你需要把它放在循环之外

var contacts = var contacts=[{"firstName":"Akira","lastName":"Laine","number":"0543236543","likes":["Pizza","Coding","Brownie Points"]},{"firstName":"Harry","lastName":"Potter","number":"0994372684","likes":["Hogwarts","Magic","Hagrid"]},{"firstName":"Kristian","lastName":"Vos","number":"unknown","likes":["JavaScript","Gaming","Foxes"]}]

function lookUpProfile(name, prop) {
  for (var i = 0; i < contacts.length; i++) {
    if (contacts[i].firstName === name) {
      if (contacts[i].hasOwnProperty(prop)) {
        return contacts[i][prop];
      } else {
        return "No such property";
      }
    }
  }
  return "No such contact";
}

console.log(lookUpProfile("Harry", "likes"));