src/constraint/weekofyear.js
function(d) {
    if (d.wyExtent) return d.wyExtent;

    // go to start of ISO week to get to the right year
    var year = later.dw.next(later.wy.start(d), 5),
        dwFirst = later.dw.val(later.Y.start(year)),
        dwLast = later.dw.val(later.Y.end(year));

    return (d.wyExtent = [1, dwFirst === 5 || dwLast === 5 ? 53 : 52]);
  }
function(d) {
    if (d.wyExtent) return d.wyExtent;

    // go to start of ISO week to get to the right year
    var year = later.dw.next(later.wy.start(d), 5),
        dwFirst = later.dw.val(later.Y.start(year)),
        dwLast = later.dw.val(later.Y.end(year));

    return (d.wyExtent = [1, dwFirst === 5 || dwLast === 5 ? 53 : 52]);
  }
function ( d ) { if ( d . wyExtent ) return d . wyExtent ; // go to start of ISO week to get to the right year var year = later . dw . next ( later . wy . start ( d ) , 5 ) , dwFirst = later . dw . val ( later . Y . start ( year ) ) , dwLast = later . dw . val ( later . Y . end ( year ) ) ; return ( d . wyExtent = [ 1 , dwFirst === 5 || dwLast === 5 ? 53 : 52 ] ) ; }
The minimum and maximum valid ISO week values for the year indicated.

@param {Date} d: The date indicating the year to find ISO values for
The minimum and maximum valid ISO week values for the year indicated .