我有这样的东西:
$scope.traveler = [
{ description: 'Senior', Amount: 50},
{ description: 'Senior', Amount: 50},
{ description: 'Adult', Amount: 75},
{ description: 'Child', Amount: 35},
{ description: 'Infant', Amount: 25 },
];
现在，为了得到这个数组的总数量，我做了这样的事情:
$scope.totalAmount = function(){
var total = 0;
for (var i = 0; i < $scope.traveler.length; i++) {
total = total + $scope.traveler[i].Amount;
}
return total;
}
当只有一个数组时，这很容易，但我有其他具有不同属性名的数组，我想要求和。
如果我能做这样的事情，我会更快乐:
$scope.traveler.Sum({ Amount });
但我不知道怎样才能在将来重复使用它:
$scope.someArray.Sum({ someProperty });
从对象数组
function getSum(array, column)
let values = array.map((item) => parseInt(item[column]) || 0)
return values.reduce((a, b) => a + b)
}
foo = [
{ a: 1, b: "" },
{ a: null, b: 2 },
{ a: 1, b: 2 },
{ a: 1, b: 2 },
]
getSum(foo, a) == 3
getSum(foo, b) == 6
如何使用Javascript和对象数组
const traveler = [
{ description: 'Senior', Amount: 50},
{ description: 'Senior', Amount: 50},
{ description: 'Adult', Amount: 75},
{ description: 'Child', Amount: 35},
{ description: 'Infant', Amount: 25 }
];
Const traveler = [
{描述:'高级'，数量:50}，
{描述:'高级'，数量:50}，
{描述:“成人”，数量:75}，
{描述:'Child'，数量:35}，
{描述:“婴儿”，数量:25}，
];
函数sum(arrayData, key){
返回arrayData.reduce((a,b) => {
返回{金额:a.金额+ b.金额}
})
｝
console.log(总和(旅行)
｀
只是另一种说法，这就是原生JavaScript函数Map和Reduce的用途(Map和Reduce是许多语言中的强大功能)。
var traveler = [{description: 'Senior', Amount: 50},
{description: 'Senior', Amount: 50},
{description: 'Adult', Amount: 75},
{description: 'Child', Amount: 35},
{description: 'Infant', Amount: 25}];
function amount(item){
return item.Amount;
}
function sum(prev, next){
return prev + next;
}
traveler.map(amount).reduce(sum);
// => 235;
// or use arrow functions
traveler.map(item => item.Amount).reduce((prev, next) => prev + next);
注意:通过创建独立的小函数，我们可以再次使用它们。
// Example of reuse.
// Get only Amounts greater than 0;
// Also, while using Javascript, stick with camelCase.
// If you do decide to go against the standards,
// then maintain your decision with all keys as in...
// { description: 'Senior', Amount: 50 }
// would be
// { Description: 'Senior', Amount: 50 };
var travelers = [{description: 'Senior', amount: 50},
{description: 'Senior', amount: 50},
{description: 'Adult', amount: 75},
{description: 'Child', amount: 35},
{description: 'Infant', amount: 0 }];
// Directly above Travelers array I changed "Amount" to "amount" to match standards.
function amount(item){
return item.amount;
}
travelers.filter(amount);
// => [{description: 'Senior', amount: 50},
// {description: 'Senior', amount: 50},
// {description: 'Adult', amount: 75},
// {description: 'Child', amount: 35}];
// Does not include "Infant" as 0 is falsey.
使用reduce和解构来求和
const traveler = [
{ description: 'Senior', Amount: 50 },
{ description: 'Senior', Amount: 50 },
{ description: 'Adult', Amount: 75 },
{ description: 'Child', Amount: 35 },
{ description: 'Infant', Amount: 25 },
];
console.log(traveler.reduce((n, {Amount}) => n + Amount, 0))
