JavaScript in Operator

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JavaScript in Operator

The in operator returns a Boolean value indicates whether the specified property is in the specified object or its prototype chain.

Note: If you set a property to undefined but do not delete it, the in operator returns true for that property.


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<!DOCTYPE html> <html> <body> <p id="point"></p> <script> var x = document.getElementById("point"); var bike = {brand: "Honda", color: "red"}; if ("model" in bike === false) bike.model = "cb1000r"; x.innerHTML = "Model : "+bike.model; </script> </body> </html>


property in object

Parameter Values

propertyRequiredA string representing a property name or array index.
objectRequiredAn object to check if it contains the property with specified name.

Return Values

trueIf the specified property is in the specified object.
falseIf the specified property is not in the specified object.


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