I want to be able to check if a container div has a child in it with an attribute of a particular value and also how many instances exist.

For example, if I had the following HTML: 

```
<div class='container'>
    <div class='child' myattr='myattrvalue1'>DIV CONTENTS</div>
    <div class='child' myattr='myattrvalue2'>DIV CONTENTS</div>
    <div class='child' myattr='myattrvalue3'>DIV CONTENTS</div>
    <div class='child' myattr='myattrvalue3'>DIV CONTENTS</div>
    <div class='child' myattr='myattrvalue3'>DIV CONTENTS</div>
    <div class='child' myattr='myattrvalue4'>DIV CONTENTS</div>
</div>

```

I would like a jquery line that that would be able to find if any div with class "child" in $(".container") has an attr of "myattr" and a value of "myattrvalue3". I would also like to be able to determine how many instances of such a child exists, which would be 3 instances of the child with myattr='myattrvalue3' in this example.