Javascript赋值变量if nil？

Question

如果一个变量的计算结果为false，在Javascript中有没有简单的赋值方法？

在ruby中，我可以这样做：

foo |= "bar"

如果foo的计算结果为false，则将"bar“赋值给foo，如下所示：(使用|=操作符)

var cars_by_brand_and_color = {};
for (var car in parking_lot) {
   // add a brand if it doesn't exist yet;
   // cars_by_brand_and_color['chevrolet'] = {};
   cars_by_brand_and_color[car['brand']] |= {};
   // and add that color to the brand if it doesn't exist yet;
   // cars_by_brand_and_color['chevrolet']['grey'] |= {}; 
   cars_by_brand_and_color[car['brand']][car['color']] |= {};
   // now let's add that car; 
   // cars_by_brand_and_color['chevrolet']['grey']['BDB-565'] = 'Mr. Smith';
   cars_by_brand_and_color[car['brand']][car['color']][car['lisence_plate']] = car['owner']
};

Answer 1

当然，JS语法是

var toAssign = mayBeNull || {};