In Parent Window
var childWin = window.open("childWin.html", "_blank", "height=400, width=550, status=yes, toolbar=no, menubar=no, location=no,addressbar=no);
//you can use the value here which has been returned by your child window
Following is my childWin HTML page. There is a button on this HTML page which when clicked will return a value to the parent window which has setValue function. Basically, child window is accessing parent's setValue function here. After this, child window is closed.
window.opener.setValue('Hello');; //I want to return true here
window.close(); //Close this child window
<button type="button" id="OKButton" onclick="OKClicked()">Click ME</button>