Operators — in and instanceof

in checks property existence, instanceof checks prototype chain

• 'key' in obj → true if the object has the key (own or inherited)
• obj instanceof Constructor → true if Constructor.prototype is in the prototype chain

Challenge: Write checkMembership() that tests:

• hasName: 'name' in { name: 'Alice' }
• hasFoo: 'foo' in { name: 'Alice' }
• isArray: [1,2,3] instanceof Array
• isDate: new Date() instanceof Date