如何遍历JSON数据

Question

The following is my JSON data in a div :

[{"Identifier":"1","Label":"10 Day","Categories":"Standard","UpdatedBy":"Lno","UpdatedAt":"01-02-2013","RefId":"0","ComType":"1","Cs":["944"],"AM":"Error Message","Message":"asdfasdf","Combiner":[{"uniqueID":"1","type":"7","rule":""}]}]

I am accessing it through a JS object:

var myArrayVar=JSON.parse(document.getElementById("populateDT").innerHTML);

I want to iterate over this JS object. The following is my code, but it doesn't access my key/value fields:

for(var i=0; i<=myArrayVar.length;i++){
    for(var j=0; j<=myArrayVar.Combiner.length; j++){
        var sessionUniqueId= myArrayVar.Combiner[j].uniqueID;
        alert(sessionUniqueId);
        var sessionType=myArrayVar.Combiner[j].type;
        alert(sessionType);
        var sessionRule=myArrayVar.Combiner[j].rule;
        alert(sessionRule);
    }
}

Can anyone suggest a solution?

Answer 1

You never use i . You need it to access the current array element, for example:

for(var j=0; j<=myArrayVar[i].Combiner.length; j++){

myArrayVar is your array, myArrayVar[i] is the i -th element in that array and myArrayVar[i].Combiner is the combiner (array) property of the i -th element.

You'll make it yourself a lot easier if you give the current element a name as well. (You probably want to come up with a less generic name such as current though.)

for(var i=0; i<myArrayVar.length;i++){
    var current=myArrayVar[i];
    for(var j=0; j<current.Combiner.length; j++){
        var sessionUniqueId=current.Combiner[j].uniqueID;
        alert(sessionUniqueId);
        var sessionType=current.Combiner[j].type;
        alert(sessionType);
        var sessionRule=current.Combiner[j].rule;
        alert(sessionRule);
    }
}

Also, i cannot equal myArrayVar.length as that index is already out of bounds. Your loop condition should have < instead of <= .

Answer 2

You have an array with one element. That element is in myArrayVar[0] and it is an object. To iterate over the object use a for ... in loop.

var myObj = myArrayVar[0];
for(var key in myObj){
    var value = myObj[key];
    console.log(key, value);
}

You should also use console.log for debugging. It will show you more information about objects than alert can.

Answer 3

for (var i = 0; i < myArrayVar.length; i++) {
    for (var j = 0; j < myArrayVar[i].Combiner.length; j++) {
        var sessionUniqueId = myArrayVar[i].Combiner[j].uniqueID;
        alert(sessionUniqueId);
        var sessionType = myArrayVar[i].Combiner[j].type;
        alert(sessionType);
        var sessionRule = myArrayVar[i].Combiner[j].rule;
        alert(sessionRule);
    }
}

Answer 4

尝试在for循环中使用“ <”代替“ <=”，并使用“ myArrayVar [i] .Combiner”代替“ myArrayVar.Combiner”。

Answer 5

There are a couple of problems I see. First, your i and j variables go one spot too far. They should be using < instead of <= .

Secondly, you're declaring variables inside the loop. That's fine, but JavaScript isn't block scoped, so you really end up with the same three variables overwriting each other as many times as there are items in the list. Your example data only has one item so you probably won't notice the overwriting problem just yet–but once you have multiple items in the list it could be a problem.