jQuery 检查 JS 对象中是否存在键
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Checking if a key exists in a JS object
提问by user2065483
I have the following JavaScript object:
我有以下 JavaScript 对象：
var obj = {
"key1" : val,
"key2" : val,
"key3" : val
}
Is there a way to check if a key exists in the array, similar to this?
有没有办法检查数组中是否存在一个键，类似于这个？
testArray = jQuery.inArray("key1", obj);
does not work.
不起作用。
Do I have to iterate through the obj like this?
我必须像这样遍历 obj 吗？
jQuery.each(obj, function(key,val)){}
回答by Sirko
Use the inoperator:
使用in运算符：
testArray = 'key1' in obj;
Sidenote: What you got there, is actually no jQuery object, but just a plain JavaScript Object.
旁注：你得到的实际上不是 jQuery 对象，而是一个普通的 JavaScript 对象。
回答by Guffa
That's not a jQuery object, it's just an object.
那不是一个 jQuery 对象，它只是一个对象。
You can use the hasOwnProperty method to check for a key:
您可以使用 hasOwnProperty 方法来检查密钥：
if (obj.hasOwnProperty("key1")) {
...
}
回答by Fernando_Jr
var obj = {
"key1" : "k1",
"key2" : "k2",
"key3" : "k3"
};
if ("key1" in obj)
console.log("has key1 in obj");
=========================================================================
================================================== ========================
To access a child key of another key
访问另一个键的子键
var obj = {
"key1": "k1",
"key2": "k2",
"key3": "k3",
"key4": {
"keyF": "kf"
}
};
if ("keyF" in obj.key4)
console.log("has keyF in obj");
回答by Ali Hallaji
Above answers are good. But this is good too and useful.
上面的答案很好。但这也很好，很有用。
!obj['your_key'] // if 'your_key' not in obj the result --> true
It's good for short style of code special in if statements:
它适用于 if 语句中的短代码风格：
if (!obj['your_key']){
// if 'your_key' not exist in obj
console.log('key not in obj');
} else {
// if 'your_key' exist in obj
console.log('key exist in obj');
}
Note: If your key be equal to null or "" your "if" statement will be wrong.
注意：如果您的键等于 null 或 ""，您的 "if" 语句将是错误的。
obj = {'a': '', 'b': null, 'd': 'value'}
!obj['a'] // result ---> true
!obj['b'] // result ---> true
!obj['c'] // result ---> true
!obj['d'] // result ---> false
So, best way for checking if a key exists in a obj is:'a' in obj
因此，检查 obj 中是否存在键的最佳方法是：'a' in obj
回答by Diablo
map.has(key)is the latest ECMAScript 2015way of checking the existance of a key in a map. Refer to thisfor complete details.
map.has(key)是ECMAScript 2015最新
的检查映射中键是否存在的方法。有关完整的详细信息，请参阅此内容。
回答by Khan
the simplest way is
最简单的方法是
const obj = {
a: 'value of a',
b: 'value of b',
c: 'value of c'
};
if(obj.a){
console.log(obj.a);
}else{
console.log('obj.a does not exist');
}回答by Achsuthan
You can try this:
你可以试试这个：
const data = {
name : "Test",
value: 12
}
if("name" in data){
//Found
}
else {
//Not found
}
