Addition and subtraction within bounds

How would you write the follo开发者_开发知识库wing in JavaScript:

    Row-=21;
    if (Row < 1) {
        Row = 1;
    }

You can do this:

Row = Math.max( Row-21, 1);

EDIT:

If you want to be able to set a minimum and/or maximum range, you could prototype your own function into Number.

Number.prototype.adjust = function( adj, min, max ) {
    if( isNaN( min ) ) min = -Infinity;
    if( isNaN( max ) ) max = Infinity;
    var res = this + ~~adj;
    return res < min ? min : res > max ? max : res;
};

Then you can use it like this:

Row = Row.adjust( -21, 1, 50 ); /* adjustment, min, max */

• 1st argument is the adjustment
• 2nd argument is the minimum range (pass null for no min)
• 3rd argument is the maximum range (pass null or leave blank for no max)

Row = Row > 22 ? Row - 21 : 1;

row-=21;
if (row < 1) {
    row = 1;
}

It seems like already-valid JS.

The only difference would be that you would need to declare your "row" variable as:

var row = 0;

Just for fun, here's a way that replaces the role of the operator with a function:

function makeBoundedOp( bound, addOrSub ){
  var newfunc = function newfunc(value,change){
    if( addOrSub === 'add' ){
       var upperbound = bound; 
       return (value+change > upperbound) ? upperbound : value+change; 
    } else {
       var lowerbound = bound;
       return (value-change < lowerbound) ? lowerbound : value-change;               
    }
  }  
  return newfunc;
}

Now build up any special-purpose bounded operator functions you need:

var subtractBoundedOne = makeBoundedOp(1,'subtract');
var subtractBoundedTen = makeBoundedOp(10,'subtract');
var addBoundedFifty = makeBoundedOp(50,'add');

Then:

var row = 20;

subtractBoundedOne(row,12); // 8
subtractBoundedTen(row,12); // 10
addBoundedFifty(row,37); // 50