将JSON对象字符串转换为值

Question

I am writing a function that takes a string, splits it, and the uses json[key][key2][key3] formatting. The problem is n is potentially infinite (not literally but needs to written that way)

function getJsonValue(json,string) {
    var vals = string.split(".");
    var x = vals.length;
    var string = '';
    while (x != 0) {
      string += "['"+vals[(vals.length-x)]+"']"
        x--
    }
    return string;
}

That will produce, for example: "['condition']['item']['condition']['temp']"

I need to extract a value from that by attaching it to a json object, like

json"['condition']['item']['condition']['temp']"

But I don't know how or if that is even possible.

Edit: The problem is I need any value from a config file to be passed in and then parsed from a returning function. Ie User knows the value will be condition.item.condition.temp for this specific query. I am trying to write one function that covers everything and pass in config values for what I know to be the output. So, on one query, I might want the condition.item.condition.temp value and on another I might want condition.wind.chill .

Answer 1

I'm not sure if I understand 100% what you're trying to do, but if you're receiving a JS object json and a string in the format field1.field2.field3 and trying to get the value of json.field1.field2.field3 then you can do something like this:

function getJsonValue(json,string) {
    var vals = string.split(".");
    for (var i = 0; i < vals.length; i++) json = json[vals[i]];
    return json;
}

It would work like this for a given object:

var obj = { field1: { field2: { field3: "Hello!" } } };
var res = getJsonValue(obj, "field1.field2.field3"); 
console.log(res); // prints Hello

Answer 2

See lodash get

_.get(json, 'key1.key2.key3')

you can build the "path" from your current code and ask lodahs to get the value out for you.

Answer 3

What about doing an eval?

var json = {
    'one': {
        'two': {
            'three': {
                'four': 4
            }
        }
    }
};

alert(eval("json['one']['two']['three']['four']"))