📝 JavaScript 检查对象中是否存在指定 key
2025-01-22 08:19:30    285 字    #前端 #📝 JavaScript
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三种方式，检查对象中是否存在指定的key。


1. in 运算符

in 运算符可以检查对象中是否存在属性。

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var person = {
    name: 'John',
    age: 30,
    city: 'New York'
};

if ('name' in person) {
    console.log('The property "name" exists in the person object.');
} else {
    console.log('The property "name" does not exist in the person object.');
}

2. hasOwnProperty 方法

hasOwnProperty 方法检查对象是否直接包含属性。

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var person = {
    name: 'John',
    age: 30,
    city: 'New York'
}

if (person.hasOwnProperty('name')) {
    console.log('The property "name" exists in the person object.');
} else {
    console.log('The property "name" does not exist in the person object.');
}

3. 使用 !== undefined 比较

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var person = {
    name: 'John',
    age: 30,
    city: 'New York'
};

if (person['name'] !== undefined) {
    console.log('The property "name" exists in the person object.');
} else {
    console.log('The property "name" does not exist in the person object.');
}

4. FAQ

  • 使用 in 和 hasOwnProperty 检查键的区别是什么？

    in 运算符检查属性是否存在于对象的原型链中，而 hasOwnProperty 检查属性是否直接存在于对象本身。