GridCalculator -- taken from https://github.com/AlphaGit/random-javascript/blob/2bb71a1af77909d564023d66623e6f54b5c2bf80/arkanoid-canvas/arkanoid.js

GridCalculator.js

// helper: grid calculator for coordinate system
function GridCalculator(realHeight, realWidth, numColumns, numRows) {
    var self = this;
    self.numColumns = numColumns;
    self.numRows = numRows;
    
    var getNumRows = function() {
    	return self.numRows;
    }
    
    var getNumColumns = function() {
    	return self.numColumns;
    }
    
    var getBlockWidth = function() {
    	return realWidth / numColumns;
    };
    
    var getBlockHeight = function() {
    	return realHeight / numRows;
    };
    
    var getBlockPosX = function(columnIndex) {
    	return columnIndex * getBlockWidth();
    };
    
    var getBlockPosY = function(rowIndex) {
    	return rowIndex * getBlockHeight();
    };
    
    var getBlockCenterPosX = function(columnIndex) {
    	return (columnIndex + 0.5) * getBlockWidth();
    };
    
    var getBlockCenterPosY = function(rowIndex) {
    	return (rowIndex + 0.5) * getBlockHeight();
    };
    
    return {
    	getBlockWidth: getBlockWidth,
    	getBlockHeight: getBlockHeight,
    	getBlockPosX: getBlockPosX,
    	getBlockPosY: getBlockPosY,
    	getBlockCenterPosX: getBlockCenterPosX,
    	getBlockCenterPosY: getBlockCenterPosY,
    	getNumRows: getNumRows,
    	getNumColumns: getNumColumns
    };
}