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 （在我的代码段底部）。

// 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。这甚至不及它如何运作。

您要做的是向对象添加新的键值对，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};

Answer 4

您可以使用 Lodash _.assign函数来实现。

library[title] = _.assign({}, {'foregrounds': foregrounds }, {'backgrounds': backgrounds });

// 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]) {

    // override one Object with the values of another (lodash)
    library[title] = _.assign({}, {
      'foregrounds': foregrounds
    }, {
      'backgrounds': backgrounds
    });
    console.log(library[title]);

    // Save to Database. Then on callback...
    // console.log('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...
    console.log('Added: <b>' + title + '</b>');
  }
}

save();

<script src="https://cdn.jsdelivr.net/npm/lodash@4.17.10/lodash.min.js"></script>

嵌套JSON：如何将新项添加（推送）到对象？

4 个答案: