localstorage:获取包含许多项的特定localstorage值

Question

在localstorage中,我有以下值的关键' 结果 ' :

[{"id":"item-1","href":"google.com","icon":"google.com"},
{"id":"item-2","href":"youtube.com","icon":"youtube.com"},
{"id":"item-3","href":"google.com","icon":"google.com"},
{"id":"item-4","href":"google.com","icon":"google.com"},
{"id":"item-5","href":"youtube.com","icon":"youtube.com"},
{"id":"item-6","href":"asos.com","icon":"asos.com"},
{"id":"item-7","href":"google.com","icon":"google.com"},
{"id":"item-8","href":"mcdonalds.com","icon":"mcdonalds.com"}]

要获得最后一项,我使用此:

// this is how I parse the arrays
var result = JSON.parse(localStorage.getItem("result")); 


for(var i=0;i<result.length;i++) {
    var item = result[i];
    $('element').val(item.href);
}

如何获取item-3或特定ID的href？

Answer 1

使用原生 Array.filter

如果您只定位现代浏览器(IE9 +或任何其他主要浏览器的最新版本),则可以使用JavaScript 1.6阵列方法filter.

var testItem,
    data = [{"id":"item-1","href":"google.com","icon":"google.com"},
{"id":"item-2","href":"youtube.com","icon":"youtube.com"},
{"id":"item-3","href":"google.com","icon":"google.com"},
{"id":"item-4","href":"google.com","icon":"google.com"},
{"id":"item-5","href":"youtube.com","icon":"youtube.com"},
{"id":"item-6","href":"asos.com","icon":"asos.com"},
{"id":"item-7","href":"google.com","icon":"google.com"},
{"id":"item-8","href":"mcdonalds.com","icon":"mcdonalds.com"}];

function getItemById(data, id) {
    // filter array down to only the item that has the id
    // https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/filter
    var ret = data.filter(function (item) {
        return item.id === id;
    });

    // Return the first item from the filtered array   
    // returns undefined if item was not found
    return ret[0];
}


testItem = getItemById(data, 'item-3');

工作实例

手动循环数据

如果你不能使用过滤器,你可能只是使用一个循环:

var testItem,
    data = [{"id":"item-1","href":"google.com","icon":"google.com"},
{"id":"item-2","href":"youtube.com","icon":"youtube.com"},
{"id":"item-3","href":"google.com","icon":"google.com"},
{"id":"item-4","href":"google.com","icon":"google.com"},
{"id":"item-5","href":"youtube.com","icon":"youtube.com"},
{"id":"item-6","href":"asos.com","icon":"asos.com"},
{"id":"item-7","href":"google.com","icon":"google.com"},
{"id":"item-8","href":"mcdonalds.com","icon":"mcdonalds.com"}];

function getItemById(data, id) {
    var i, len;
    for (i = 0, len = data.length; i < len; i += 1) {
        if(id === data[i].id) {
            return data[i];
        }
    }

    return undefined;
}

testItem = getItemById(data, 'item-3');

工作实例

尽管使用循环强制它可能看起来不如使用优雅Array.filter,但事实证明在大多数情况下循环比快Array.filter.

重构为对象而不是数组

假设id您的每个项目都是唯一的,那么最好的解决方案就是重构您存储数据的方式.而不是对象数组,使用一个对象,该对象使用id键作为键来存储包含href和icon键/属性值的对象.

var data = {
    "item-1": {"href": "google.com", "icon": "google.com"},
    "item-2": {"href": "youtube.com", "icon": "youtube.com"},
    "item-3": {"href": "google.com", "icon": "google.com"},
    "item-4": {"href": "google.com", "icon": "google.com"},
    "item-5": {"href": "youtube.com", "icon": "youtube.com"},
    "item-6": {"href": "asos.com", "icon": "asos.com"},
    "item-7": {"href": "google.com", "icon": "google.com"},
    "item-8": {"href": "mcdonalds.com", "icon": "mcdonalds.com"}
};

这将使访问项目变得更加容易和快捷:

var data = JSON.parse(localStorage.getItem("result")); 
data["item-3"].href;