hasOwnProperty in JavaScript

Question

Consider  function Shape         this name    quot Generic quot       this draw   function             return  quot Drawing  quot    this name    quot  Shape quot             function welcomeMessage         var shape1   new Shape          alert shape1 draw         alert shape1 hasOwnProperty name        This is returning false     welcomeMessage called on the body onload event  I expected shape1 hasOwnProperty name  to return true  but it s returning false  What is the correct behavior

User · Accepted Answer

hasOwnProperty is a normal JavaScript function that takes a string argument  When you call shape1 hasOwnProperty name  you are passing it the value of the name variable  which doesn t exist   just as it would if you wrote alert name   You need to call hasOwnProperty with a string containing name  like this  shape1 hasOwnProperty  quot name quot

User · Answer

hasOwnProperty   is a nice property to validate object keys  Example  var obj    a 1  b 2    obj hasOwnProperty  a      true

User · Answer

hasOwnProperty expects the property name as a string  so it would be shape1 hasOwnProperty  name

User · Answer

Try this    function welcomeMessage         var shape1   new Shape          alert shape1 draw         alert shape1 hasOwnProperty  name         When working with reflection in JavaScript  member objects are always refered to as the name as a string  For example   for i in obj           The loop iterator i will be hold a string value with the name of the property  To use that in code you have to address the property using the array operator like this     for i in obj       alert  The value of obj     i           obj i

[javascript] hasOwnProperty in JavaScript

Examples related to javascript