CODEWITHSUNDEEP
javascriptfunctionobject
Mohammad Faizan khan
Mohammad Faizan khan

Reputation: 1235

property value have changed but not effected

<script>

           var Faizan = {
               isSharp: true,
               use: function(){
                 return this.isSharp = "Dangerous"//!this.isSharp;
               }
           };
           console.log(Faizan.use());
           console.log( !Faizan.isSharp, "Verify the value of isSharp has been changed." );
       </script>

Output of the above script is 1.Dangerous 2.False 1st output is very sample as i expected it but second output is surprisingly false Why? when isSharp is change to Dangerous then Why !Faizan.isSharp Returning False?? isSharp value have changed

Upvotes: 0

Views: 42

Answers (1)

Adrian Baran
Adrian Baran

Reputation: 895

As @Sacho said "!" is the logical NOT operator, so:

  p   |  !p
-------------
true  | false 
false | true

In JavaScript non-empty string will evaluate to true if tested, see example below:

var simpleText = "This is simple text";
if (simpleText) {
  console.log("The value is truthy");
} else {
  console.log("The value is falsy");
}
// => The value is truthy

And empty string will evalute to false:

var emptyText = "";
if (emptyText) {
  console.log("The value is truthy");
} else {
  console.log("The value is falsy");
} 
// => The value is falsy

You can read more about that here: http://www.sitepoint.com/javascript-truthy-falsy/

TL;DR

Your statement !Faizan.isSharp is equal to !true which is equal to false.

Upvotes: 2

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