在推送之前敲除检查 observableArray 中是否存在

Question

我是 Knockout 的新手，我有一个小问题阻止我完成我的简单项目。
我有一个名为 loanDeductions 的 observableArray，我显示在一个带有 foreach 绑定的表中。
I have another observableArray called loanDeductionsList which is also from the json data of my first observableArray, I used it in my drop down list which when a value is selected, it will push the selected data to我的桌子。如果它没有意义，因为我无法真正清楚地解释它，这是我的 javascript 文件：

var deductionLine = function (deductionID, deductionName, amount) {
    self = this;
    self.deductionID = ko.observable(deductionID);
    self.deductionName = ko.observable(deductionName);
    self.amount = ko.observable(formatCurrency(amount));
};

function LoanDeductions(deductions) {
    var self = this;
    self.loanDeductions = ko.observableArray(ko.utils.arrayMap(deductions, function (deduction) {
        return new deductionLine(deduction.deductionID, deduction.deductionName, deduction.amount)
    }));
    self.loanDeductionsList = ko.observableArray(ko.utils.arrayMap(deductions, function (deduction) {
        return new deductionLine(deduction.deductionID, deduction.deductionName, deduction.amount)
    }));

    self.selectedDeduction = ko.observable();

    self.selectedDeduction.subscribe(function (data) {
        self.loanDeductions.push({
            deductionID: data.deductionID,
            deductionName: data.deductionName,
            amount: data.amount,
        });
    });
}

你能帮我找到一种方法，让我的函数 selectedDeduction.subscribe() 仅在要推送的项目不存在于我的 loanDeductions observableArray 时推送数据。
任何帮助将不胜感激。谢谢！

我有点意识到我填充下拉列表的方式可能不是最好的方式，我愿意建议更好的方式并重写我的程序。

Answer 1

只是为了分享我所做的，我在 selectedDeduction.subscribe() 中添加了这一行：

self.selectedDeduction.subscribe(function (data) {
        var match = ko.utils.arrayFirst(self.loanDeductions(), function(deduction) {
            return deduction.deductionID() === data.deductionID(); 
        });
        if (match) {
            alert(data.deductionName() + ' already exists!');
        } else {
            self.loanDeductions.push({
                deductionID: data.deductionID,
                deductionName: data.deductionName,
                amount: data.amount,
            });
            }
});