Info

These test if a property exists in an object. The boolean syntax is often used, but can lead to wrong results (a property with a value of false wouldn't be detected, for example).

Preparation code

<script>
  var obj = {
    a: 1
  };
</script>

Test runner

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if ('a' in obj) {};
if ('b' in obj) {};

if (obj.a) {};
if (obj.b) {};

if (obj.hasOwnProperty('a')) {};
if (obj.hasOwnProperty('b')) {};

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Revisions

You can edit these tests or add even more tests to this page by appending /edit to the URL. Here’s a list of current revisions for this page:

• Revision 1: published by Thomas Fuchs on 14th August 2010
• Revision 2: published on 14th August 2010
• Revision 3: published by Thomas Fuchs on 14th August 2010
• Revision 4: published on 14th August 2010
• Revision 5: published by Tom on 14th August 2010
• Revision 12: published by Mourner on 10th September 2010
• Revision 13: published on 20th April 2011

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