Jak sprawdzić, czy obiekt ma kluczowy JavaScript
myObj.hasOwnProperty('key') // it checks object for particular key and not on prototype
Proud Pony
myObj.hasOwnProperty('key') // it checks object for particular key and not on prototype if ('key' in myObj)
// better
if (!myObj.hasOwnProperty('key'))"key" in obj // true, regardless of the actual value
If you want to check if a key doesn't exist, remember to use parenthesis:
!("key" in obj) // true if "key" doesn't exist in object
!"key" in obj // ERROR! Equivalent to "false in obj"
Or, if you want to particularly test for properties of the object instance (and not inherited properties), use hasOwnProperty:
obj.hasOwnProperty("key") // trueif ('key' in myObj)if (myObj['key']) {
// Do something
}Object.prototype.hasOwnProperty()