Javascript hasOwnProperty method & in keyword _javascript tips

This method cannot check whether the object's prototype chain has this property, which must be a member of the object itself.
The in operation checks whether the object is named property. You can also examine the object's prototype to determine whether the property is part of the prototype chain.

Copy Code code as follows:

function Test () {
This. A= ' abc ';
}
test.prototype.b= ' EFG ';

var test=new test;
Alert (Test.hasownproperty (' a '));//Output True
Alert (Test.hasownproperty (' B '));//Output False

Alert (' A ' in test);//Output True
Alert (' B ' in test);//Output True