js 计算对象数组中某个属性合计

countTotal调用示例：

let arr = [
	{id: 0, price: 199.88},
	{id: 1, price: 299.88},
	{id: 2, price: 399.88}
];
console.log(countTotal(arr, 'price')); //899.64

　　

//计算对象数组中某个属性合计
function countTotal(arr, keyName) {
	let $total = 0;
	$total = arr.reduce(function (total, currentValue, currentIndex, arr){
	    return currentValue[keyName] ? (total + currentValue[keyName]) : total;
	}, 0);
	return $total;
}