嵌套JSON:如何将新项添加(推送)到对象？

Question

我刚开始使用Arrays,Objects和JSON - 所以希望我能在这里看到一些简单的东西.我在尝试将新项目添加(推送)到我的json对象时遇到错误.

我遇到以下错误:( Result of expression 'library.push' [undefined] is not a function 在我的代码片段的底部).

// This is my JSON object generated from a database
var library = {
    "Gold Rush" : {
        "foregrounds" : ["Slide 1","Slide 2","Slide 3"],
        "backgrounds" : ["1.jpg","","2.jpg"]
    },
    "California" : {
        "foregrounds" : ["Slide 1","Slide 2","Slide 3"],
        "backgrounds" : ["3.jpg","4.jpg","5.jpg"]
    }
}

// These will be dynamically generated vars from editor
var title = "Gold Rush";
var foregrounds = ["Howdy","Slide 2"];
var backgrounds = ["1.jpg",""];

function save () {

    // If title already exists, modify item
    if (library[title]) {
        // Replace values with new
        library[title].foregrounds = foregrounds;
        library[title].backgrounds = backgrounds;

        // Save to Database. Then on callback...
        document.write('Changes Saved to <b>'+title+'</b>');

    // If title does not exist, add new item
    else {
        // Format it for the JSON object
        var item = ('"'+title+'" : {"foregrounds" : '+foregrounds+',"backgrounds" : '+backgrounds+'}');


        // THE PROBLEM SEEMS TO BE HERE??
        // Error: "Result of expression 'library.push' [undefined] is not a function"
        library.push(item);


        // Save to Database. Then on callback...
        document.write('Added: <b>'+title+'</b>');
    }
}

save();

Answer 1

library是一个对象,而不是一个数组.你把东西推到了数组上.与PHP不同,Javascript有所区别.

您的代码尝试创建一个看起来像键值对的源代码的字符串,然后将其"推"到该对象上.这甚至没有接近它的工作原理.

您要做的是向对象添加一个新的键值对,其中键是标题,值是另一个对象.看起来像这样:

library[title] = {"foregrounds" : foregrounds, "backgrounds" : backgrounds};

"JSON对象"是一个模糊的术语.您必须小心区分程序内存中的实际对象和JSON格式的文本片段.

Answer 2

如果您的JSON没有密钥,您可以这样做:

library[library.length] = {"foregrounds" : foregrounds,"backgrounds" : backgrounds};

所以,试试这个:

var library = {[{
    "title"       : "Gold Rush",
        "foregrounds" : ["Slide 1","Slide 2","Slide 3"],
        "backgrounds" : ["1.jpg","","2.jpg"]
    }, {
    "title"       : California",
        "foregrounds" : ["Slide 1","Slide 2","Slide 3"],
        "backgrounds" : ["3.jpg","4.jpg","5.jpg"]
    }]
}

然后:

library[library.length] = {"title" : "Gold Rush", "foregrounds" : ["Howdy","Slide 2"], "backgrounds" : ["1.jpg",""]};

Answer 3

push是一个Array方法,对于json对象,您可能需要定义它

这应该这样做:

library[title] = {"foregrounds" : foregrounds,"backgrounds" : backgrounds};