javascript - 主干集合 : Retrieve distinct values of a collection and sum the distinct values

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给出这个“样本收集数据”:

[{brand:'audi', amount: '100.16', id:'1234'},
{brand:'audi', amount: '67.84', id:'3456'},
{brand:'bmw', amount: '80.70', id:'3456'}]

我如何添加集合中不同品牌的数量？

并获取此数据:

[{brand:'audi', amount: '168.00'},
{brand:'bmw', amount: '80.70'}]

在此先感谢大家!

Answer 1

这是一个相当标准的 reduce这只是简单的 JavaScript:

var o = data.reduce(function(m, e) {
    // There are lots of ways to do this depending on what sorts
    // of things are going to be values in `m`, we're expecting
    // the values to be non-zero numbers so a simple `!` is fine.
    if(!m[e.brand])
        m[e.brand] = 0;
    m[e.brand] += parseFloat(e.amount);
    return m;
}, { });

如果您担心石器时代的浏览器，请使用 _(data).reduce 或一个简单的循环:

var o = { }, i;
for(i = 0; i < data.length; ++i) {
    if(!o[data[i].brand])
        o[data[i].brand] = 0;
    o[data[i].brand] += parseFloat(data[i].amount]);
}

只要浮点值都很小并且像它们一样靠得很近，您就应该非常安全地使用浮点值。