使用 for 循环 JS 遍历数组

Question

我有一个对象数组 (contacts)，我需要编写一个函数来检查 firstName （函数的第一个参数） 是否是实际联系人的 firstName并且给定的属性 （prop 是函数的第二个参数） 是该联系人的属性。如果两者都为真，则返回该属性的“值”。

如果 firstName 不对应任何联系人，则返回 “No such contact”

如果 prop 不对应任何有效属性，则返回 "No such property"

我知道我需要做什么，我写的 sudo 但是用实际的 JavaScript 写它我遇到了阻塞。

以下是我目前所写的：

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 lookUpProfile(firstName, prop) {
    var value;
    for (i = 0; i < 2; i++) {
        if (contacts[i].firstName === true && contacts[i].prop === true) {
            value = contacts[i].prop;
            return value;
        }
    }
}

Answer 1

您可以在找到具有给定firstName 的联系人后使用中断循环，然后检查传递的prop 值并相应地返回消息。

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 lookUpProfile(firstName, prop) {
    var value = undefined;
    for (i = 0; i < contacts.length; i++) {
        if (contacts[i].firstName === firstName) {
            value = contacts[i];
            break;
        }
    }
    
    if(!value) {
        return 'No such contact';
    }
    
    if(!(prop in value)) {
        return 'No such property';
    }

    return value[prop];
}
console.log(lookUpProfile('Sherlock', 'likes'));
console.log(lookUpProfile('Harry', 'friends'));
console.log(lookUpProfile('John', 'likes'));

Answer 2

您可以使用array.prototype.find检查该联系人是否存在于数组中：

var contacts = [{firstname: "aaa", prop1: "val1"}, {firstname: "bbb", prop2: "val2"}];

function yourFunc(firstname, prop) {
  var ct = contacts.find(c => c.firstname === firstname);
  return ct ? ct[prop] || "No such property" : "No such contact";
}

console.log(yourFunc("aaa", 'prop2'));
console.log(yourFunc("aaa", 'prop1'));
console.log(yourFunc("bbb", 'prop2'));
console.log(yourFunc("bbb", 'prop1'));
console.log(yourFunc("ccc", 'prop1'));

Answer 3

使用 For 循环语句，应该是这样的：

function lookUpProfile(firstName, prop) {
    var contact;
    for (var i = 0; i < contacts.length; i++) {
       if (contacts[i].firstName === firstName){
         contact = contacts[i];
         break;
       }
    }
    return contact ? ( contact[prop] ? contact[prop] : 'No such property') : 'No such contact';
}

Answer 4

function lookUpProfile(firstName, prop) {
    var contact;
    for (i = 0; i < contacts.length; i++) {
        if (contacts[i].firstName === firstName) {
            contact = contacts[i];
            break;
        }
    }

    if(!contact) {
        return 'No such contact';
    }

    if(!contact[prop]) {
        return 'No such property';
    }

    return contact[prop];
}