javascript - 为什么我使用 jQuery 获取 [object object]？

Question

我有一个函数，我想尝试使用如下所示的变量对两个数字求和，但我得到的是 [object object] 而不是总和。

 
var convenienceCharge = 100;
var totalPgCost = 500;
var subTotalPgCost = 0;

function totalPgCostFunction() {

subTotalPgCost += $('.subTotalPgCost').text(convenienceCharge +  totalPgCost + 18);

alert(subTotalPgCost);
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>

<button onclick="totalPgCostFunction();">Click</button>

Answer 1

.text 将返回一个对象。这就是为什么你看到[object object]

你需要这样做。

var convenienceCharge = 100;
var totalPgCost = 500;
var subTotalPgCost = 0;

function totalPgCostFunction() {

subTotalPgCost += convenienceCharge +  totalPgCost + 18;

$('.subTotalPgCost').text(subTotalPgCost);
alert(subTotalPgCost);
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>

<button onclick="totalPgCostFunction();">Click</button>
<div class="subTotalPgCost"></div>