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JavaScript - check if key exists in object
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In this article, we would like to show you how to check if key exists in object working with JavaScript.
Quick solution:
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var object = { keyName: 'A'};2
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console.log('keyName' in object); // true
In this example, we use for...in statement to check if a key exists in the object. This way true value is returned even when the key value is undefined.
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var object = { keyName1: 'A', keyName2: undefined };2
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console.log('keyName1' in object); // true4
console.log('keyName2' in object); // true (key exists but value is undefined)5
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console.log('keyName3' in object); // falseYou can also use hasOwnProperty() method to achieve the same result as above.
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var object = { keyName1: 'A', keyName2: undefined };2
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console.log(object.hasOwnProperty('keyName1')); // true4
console.log(object.hasOwnProperty('keyName2')); // true5
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console.log(object.hasOwnProperty('keyName3')); // false