Remove non-numbers in JS, keep at most one decimal place

 // Remove non-numbers 
   var clearNoNum = function (item) {
         if (item!=null && item!=undefined ) {
             // Replace all non-numbers first, except numbers and . 
            item = item.replace(/[^ \d.]/g, "" );
             // must ensure that the first one is a number instead of. 
            item = item.replace(/^\./g, "" );
             // guarantee that only one appears. Not many 
            Item = item.replace(/\.{ 2 , }/g, ​​"" );
             // Guaranteed. Only appears once, not more than twice 
            item = item.replace( " . " , " $#$ ").replace(/\./g, "" ).replace( " $#$ " , " . " );
             // keep at most one decimal place 
            var arr = item.split( " . " );
             if (arr .length > 1 ) item = arr[ 0 ] + ' . ' + (arr[ 1 ].length > 1 ? arr[ 1 ].substr( 0 , 1 ) : arr[ 1 ]);
         }
        return item;
    }