console.log(1 in a) // return true console.log('1' in a) // return false const b = Object.create(a) // this will add a as parent of b console.log(b.hasOwnProperty(1)) // return true Using in operator - The in operator returns true if the specified property is in the specified object or its prototype chain i.e inside in its parent. What if we have hasOwnProperty as a property name in an object? Comment your thoughts below.Ģ. Note: hasOwnProperty returns true even if the value of the property is null or undefined. This method returns a boolean indicating whether the object has the specified property as its own property, not the parent/inheriting property.Ĭonsole.log(a.hasOwnProperty(1)) // return true console.log(a.hasOwnProperty('1')) // return false const b = Object.create(a) // this will add a as parent of b console.log(b.hasOwnProperty(1)) // return false There are three ways to check the property exists in an object or not. How to check properties existence in an object const data = Object.entries(a) // returns, ,, ]įrom what we see above order of appearance of properties is not fixed in an object. const keys = Object.values(a) // return ģ. Rreturns an array of string keys.Ĭonst keys = Object.keys(a) // return const newKeys = Object.getOwnPropertyNames(a) // return keys.map(key => console.log(a)) // return Ģ.
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