[英]Get key of a hashmap withou know it's name
Having one only key/value into an object, how to get them without know the key name? 在对象中只有一个键/值,如何在不知道键名的情况下获取它们? (If it's possible) (如果它是可能的)
var m = {x:5}; // we don't know x is the key
You can use hasOwnProperty
for things like this https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Object/HasOwnProperty 您可以将hasOwnProperty
用于此类https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Object/HasOwnProperty
var m = {x:5};
function keys(obj)
{
var keys = [];
for(var key in obj)
{
if(obj.hasOwnProperty(key)) {
{
keys.push(key);
}
}
return keys;
}
console.log(m);
So using this knowledge, you can write a function that basically checks whether a given key exists in an object: 因此,使用此知识,您可以编写一个函数,该函数基本上检查对象中是否存在给定键:
function hasKey(obj, key) {
return obj.hasOwnProperty(key);
}
An alternative to for…in
loop, if the browser support ES5 (or has a shim for ES5): 如果浏览器支持ES5(或具有ES5的填充程序),则for…in
循环的替代方法:
var key = Object.keys(m)[0];
See: https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Object/keys 参见: https : //developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Object/keys
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