如何声明JSON并对其进行迭代

使用for (variable in object)时，它将variable设置为对象的键，而不是值。要访问这些值，必须使用object[variable]。所以在你的情况下，它应该是：

for (var rowCtr in a.imageTable) {
    var obj = a.imageTable[rowCtr];

如果变量imageTable引用了发布的json，那么您将使用id迭代包含对象的数组，如下所示：

var array = imageTable.image1; // or image2, image3
for(var i=0;i<array.length;i++){
    console.log(array[i].id); //  wil output table, computer, ac
}

var imageTable = {
           "image1" :  [{
                "id": "table",
                "source": "http://test.reinventio.tk/office-space-game-3/images/table.jpg",
                "alert": [],
                "explanation": "Tables are needed for maintaining a good posture and consequently, 'n good health - an entrepreneur cant function with a perpetually aching 'n back now, can he?"           
            }, {
                "id": "computer",
                "source": "http://test.reinventio.tk/office-space-game-3/images/computer.jpg",
                "alert": [],
                "explanation": "Whats work without a computer?"
            }, {
                "id": "ac",
                "source": "http://test.reinventio.tk/office-space-game-3/images/ac.jpg",
                "alert": [],
                "explanation": "Air cons are luxuries. Besides, 'nas an entrepreneur, 'nyoure supposed to be sweating it out!"
            }],
            "image2" :  [{
                "id": "sofa",
                "source": "http://test.reinventio.tk/office-space-game-3/images/sofa.jpg",
                "alert": [],
                "explanation": "Sofas are a luxury. Besides, 'nstartups are all but cozy and cusiony, like a sofa!"
            }, {
                "id": "xbox",
                "source": "http://test.reinventio.tk/office-space-game-3/images/xbox.jpg",
                "alert": [],
                "explanation": "Gaming in the office space is a strict no-no.'n For an entrepreneur, work itself is play!"
            }, {
                "id": "whiteboard",
                "source": "http://test.reinventio.tk/office-space-game-3/images/whiteboard.jpg",
                "alert": [],
                "explanation": "Wall emulsion paint turns all your walls'n into gigantic whiteboards. So why waste money 'non a small one?"
            }],
            "image3" : [{
                "id": "pool",
                "source": "http://test.reinventio.tk/office-space-game-3/images/pooltable.jpg",
                "alert": [],
                "explanation": "Pool-dreams are to be dreamt after your startup grows."
            }, {
                "id": "green",
                "source": "http://test.reinventio.tk/office-space-game-3/images/inofficeplant.jpg",
                "alert": [],
                "explanation": "Landscaping in the office?'n Lifes not a golf course - especially 'nfor a startup."
            }, {
                "id": "paper",
                "source": "http://test.reinventio.tk/office-space-game-3/images/paper.jpg",
                "alert": [],
                "explanation": "Be a jugaadu and improvise to save costs 'n- why would you want to buy paper when you can use the empty side'n of election pamphlets?"
            }]
};
var array = imageTable.image1; // or image2, image3
for(var i=0;i<array.length;i++){
    console.log(array[i].id); //  wil output table, computer, ac
}

您可以将其扩展为使用嵌套循环迭代所有imageX对象

var keys = Object.keys(imageTable);
for(var i=0;i<keys.length;i++){
    var array = imageTable[keys[i]];
    for(var j=0;j<array.length;j++){
        console.log(array[j].id); //  wil output table, computer, ac, sofa, xbox etc
    }
}

var imageTable = {
           "image1" :  [{
                "id": "table",
                "source": "http://test.reinventio.tk/office-space-game-3/images/table.jpg",
                "alert": [],
                "explanation": "Tables are needed for maintaining a good posture and consequently, 'n good health - an entrepreneur cant function with a perpetually aching 'n back now, can he?"           
            }, {
                "id": "computer",
                "source": "http://test.reinventio.tk/office-space-game-3/images/computer.jpg",
                "alert": [],
                "explanation": "Whats work without a computer?"
            }, {
                "id": "ac",
                "source": "http://test.reinventio.tk/office-space-game-3/images/ac.jpg",
                "alert": [],
                "explanation": "Air cons are luxuries. Besides, 'nas an entrepreneur, 'nyoure supposed to be sweating it out!"
            }],
            "image2" :  [{
                "id": "sofa",
                "source": "http://test.reinventio.tk/office-space-game-3/images/sofa.jpg",
                "alert": [],
                "explanation": "Sofas are a luxury. Besides, 'nstartups are all but cozy and cusiony, like a sofa!"
            }, {
                "id": "xbox",
                "source": "http://test.reinventio.tk/office-space-game-3/images/xbox.jpg",
                "alert": [],
                "explanation": "Gaming in the office space is a strict no-no.'n For an entrepreneur, work itself is play!"
            }, {
                "id": "whiteboard",
                "source": "http://test.reinventio.tk/office-space-game-3/images/whiteboard.jpg",
                "alert": [],
                "explanation": "Wall emulsion paint turns all your walls'n into gigantic whiteboards. So why waste money 'non a small one?"
            }],
            "image3" : [{
                "id": "pool",
                "source": "http://test.reinventio.tk/office-space-game-3/images/pooltable.jpg",
                "alert": [],
                "explanation": "Pool-dreams are to be dreamt after your startup grows."
            }, {
                "id": "green",
                "source": "http://test.reinventio.tk/office-space-game-3/images/inofficeplant.jpg",
                "alert": [],
                "explanation": "Landscaping in the office?'n Lifes not a golf course - especially 'nfor a startup."
            }, {
                "id": "paper",
                "source": "http://test.reinventio.tk/office-space-game-3/images/paper.jpg",
                "alert": [],
                "explanation": "Be a jugaadu and improvise to save costs 'n- why would you want to buy paper when you can use the empty side'n of election pamphlets?"
            }]
};
var keys = Object.keys(imageTable);
for(var i=0;i<keys.length;i++){
    var array = imageTable[keys[i]];
    for(var j=0;j<array.length;j++){
        console.log(array[j].id); //  wil output table, computer, ac, sofa, xbox etc
    }
}

像这样，您可以访问每个主题的id和源

var id = []; 
var src= [];
for (var rowCtr in a.imageTable) {
        id= a.imageTable[rowCtr].id;
        src= a.imageTable[rowCtr].source;
}