Jquery .when() and .then() not working?

I had try something with the below:

$.when($(smtg).fadeOut(300)).then($(smtg).fadeIn(300));

What's wrong with it while the document at http://api.jquery.com/jQuery.whe开发者_JAVA技巧n/ Chrome console says Uncaught type error: has no method when

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Edit: You need jQuery 1.5+

OR simply do this:

$(smtg).fadeOut(300, function() {
    $(smtg).fadeIn(300);
});

This basically runs the fadeOut first, once the animation is done then it will run the callback function in our case the fadeIn

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Simplest possibility, you are using an older (than 1.5) version of jQuery.