是否有可能在JavaScript对象文字中循环

Question

So this is my question (maybe stupid), is there any possible to do this:

 var data {
     "label" : value,
     "sets" : [             
         for (var i=0; i < item.length; i++)
         {
             somedata: "data"   
         }
     ]  
 }

to reach result:

 var data {
     "label" : value,
     "sets" : [  
         {
            somedata: "data1"
         },
         {
            somedata: "data2"
         }
     ]  
 }

Much thx for help.

Answer 1

As jimm101 has pointed out , you are not working with JSON, that's just JavaScript (the var in there proves it) . If you want to calculate a value inside a literal JavaScript object, you can use an immediately invoked function

var data = {
     "label" : value,
     "sets" : (function(){
         var arr = [];
         for (var i=0; i < item.length; i++) {
             arr.push( {somedata: "data" + i} ) ;
         }
         return arr;
      })()
 };

As dystroy has pointed out You can also use Array.map to return a transformed array, without needing an immediately invoked function, which looks a little nicer

Answer 2

You may use functional programming :

var data = {
  "label" : "value",
  "sets" : item.map(function(_,i){ return {somedata: "data"+(i+1)} })  
}

Answer 3

Use the following:

var data = {
    label: value,
    get sets(){
        var array = [];
        /* write your logic to fill the array here. */
        return array;
    }
}

Reference here

Answer 4

As others have commented, JSON is data, not code. It looks like you're making javascript code though, since JSON also wouldn't include the var data part.

• JSON => JavaScript Object Notation, a wide-spread way of representing data.
• javascsript object => A structure within the javascript programming language that uses JavaScript Object Notation.

You can do something like this.

var data = {
    "label" : 'my_label',
};

item = ['one','two','another'];
data.sets = [];
for (var i=0; i < item.length; i++)
{
    data.sets.push({'somedata': item[i]});
}

Answer 5

You can use array comprehension ( https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Array_comprehensions ), but it's not supported yet by all browsers (ECMAScript 6).

var value = "test";
var item = ["data1", "data2", "data3"];

var data = {
    "label" : value,
    "sets" : [for (x of item) {somedata: x}]
};

/*
    Result : 

    data = {
        "label":"test",
        "sets":[
            {"somedata":"data1"},
            {"somedata":"data2"},
            {"somedata":"data3"}
        ]
    }
*/

Answer 6

You can have nested data in JSON like for example

var myObject = {
  "first": "John",
  "last": "Doe",
  "age": 39,
  "sex": "M",
  "salary": 70000,
  "registered": true,
  "interests": [ "Reading", "Mountain Biking", "Hacking" ],
  "favorites": {
    "color": "Blue",
    "sport": "Soccer",
    "food": "Spaghetti"
  }, 
  "skills": [
    {
      "category": "JavaScript",
      "tests": [
        { "name": "One", "score": 90 },
        { "name": "Two", "score": 96 }
      ] 
    },
    {
      "category": "CouchDB",
      "tests": [
        { "name": "One", "score": 79 },
        { "name": "Two", "score": 84 }
      ] 
    },
    {
      "category": "Node.js",
      "tests": [
        { "name": "One", "score": 97 },
        { "name": "Two", "score": 93 }
      ] 
    }
  ]
};

You can access such an array and its contents using a loop in your program

Source: http://www.json.com/