javascript - 在 JavaScript 中插入或更新对象

Question

我正在尝试在 JavaScript 中构建一个对象，但根据产品 ID 是否已存在来更新或创建属性。我有:

var model = [];

$('.glyphicon-plus').click(function() {
    var product_id = $('#productSelect').val();
    var size_id = $('#sizeSelect').val();
    var colour_id = $('#colourSelect').val();
    var quantity = $('#quantity').val();
    if (i = subFilter(model, "product_id", product_id) !== false) {
        if (i = subFilter(model, "size_id", size_id) !== false) {
            if (i = subFilter(model, "colour_id", colour_id) !== false) {
                console.log(model);
                model.i.quantity = quantity;
            }
        }
    }
    model.push({
        product_id: product_id,
        size_id: size_id,
        colour_id: colour_id,
        quantity: quantity
    });
    subFilter(model, "product_id", product_id);
    console.log(model)
});

function subFilter(object, paramName, paramValue) {
    $.each(object, function(i, v) {
        if (v[paramName] == paramValue) {
            return i;
        }
    });
}

但我得到:

Uncaught TypeError: Cannot set property 'quantity' of undefined

如何正确构建此对象，插入新的“记录”或更新该对象(如果已存在)？

Answer 1

改变

model.i.quantity = quantity;

至

model[i].quantity = quantity;

要访问对象的动态属性，请使用数组表示法。

.i 将在对象 model 中搜索键 'i'，而在 model[i] 中> 首先替换i的值，然后在model对象中搜索key。

<小时/>

更新:

问题中的代码包含许多错误。尝试以下代码。

var model = [];

$('.glyphicon-plus').click(function () {
    var product_id = $('#productSelect').val(),
        size_id = $('#sizeSelect').val(),
        colour_id = $('#colourSelect').val(),
        quantity = $('#quantity').val();

    // Get index of the element where all the fields matches
    var index = getObjectIndex(model, product_id, size_id, colour_id);

    // If object found in the array
    if(index !== false) {
        // Update the quantity in the same element
        model[index].quantity = quantity;
    } else {
        // Add the element in the array
        model.push({
            product_id: product_id,
            size_id: size_id,
            colour_id: colour_id,
            quantity: quantity
        });
    }
});

// Currently the function is Static, but it can be changed to dynamic
// by using nested loop and a flag to store the match status
function getObjectIndex(arr, product_id, size_id, colour_id) {
    // Loop over array to find the matching element/object
    for(var i = 0; i < arr.length; i++) {
        var obj = arr[i];
        if(obj.product_id === product_id && obj.size_id === size_id && obj.colour_id === colour_id) {
            // When all key-value matches return the array index
            return i;
        }
    }

    // When no match found, return false
    return false;
}