从json数据中选择特定的键

Question

I have a array as:

var cols = ["ticker", "highPrice", "lowPrice","lastPrice"] // dynamic

Json data comming from backend as:

info = {ticker: "AAPL", marketCap: 2800000000, lowPrice: 42.72, highPrice: 42.84}

suppose I want to select market cap then I can do info.marketCap . But I want to select only those json values which keys are equals to cols ie info.ticker, info.highPrice, info.lowPrice

and assign N/A to those which is undefined in json but present in cols array ie info.lastPrice = "N/A"

Note: cols changes from time to time

Here is what I have got so far

SyScreener.fillScreenerResult = function(info) {
        var cols = ["ticker", "highPrice", "lowPrice", "openPrice", "lastPrice", "currentVol", "avgVol"];
        var data = [];
        for(var i=0; i<info.length; i++) {
            var jsonKeys = Object.keys(info[i]);
            for(var j=0; j<jsonKeys.length; i++) {
                if(cols.contains(jsonKey[j])) {
                    // TODO something like - data.push([info[i].jsonKey[j])
                } else {
                    // TODO something like - info[i].colsValue = "N/A"
                }
            }
        }
        SyUtils.createDataTable("screener_result", data);   
    };

Answer 1

do you mean something like this:

var cols = ["ticker", "highPrice", "lowPrice","lastPrice"];
info = {ticker: "AAPL", marketCap: 2800000000, lowPrice: 42.72, highPrice: 42.84};
for(var c = 0, clen = cols.length; c < clen; c++) {
  if( !(cols[c] in info) ) {
     console.log("N/A");
  }
  else {
    console.log(info[cols[c]]);
  }
}

Demo:: jsFiddle

Answer 2

I may not be reading your question correctly but from my understanding I might suggest something like this.

for (var i=0; i<cols.length; i++) {
    var fieldName = cols[i];
    if (!info.hasOwnProperty(fieldName)) {
        info[fieldName] = 'N/A';
    }
}

This simply iterates through each field name in cols and checks if it is a property of the info JSON object. If it isn't already present the loop adds the property with a value of 'N/A'.

Answer 3

var cols = ["ticker", "highPrice", "lowPrice","lastPrice"]

var info = {ticker: "AAPL", marketCap: 2800000000, lowPrice: 42.72, highPrice: 42.84}

var output = {};
for(each in info) {
    var index = cols.indexOf(each)
    if(index != -1) {
        output[each] = info[each];
        //remove extra already checked element
        cols.splice(index,1)
    }
}
//append remaining keys
for(var i=0;i<cols.length;i++) {
    output[cols[i]] = "N/A"
}

console.log(output)
//output Object {ticker: "AAPL", lowPrice: 42.72, highPrice: 42.84, lastPrice: "N/A"} 

Answer 4

First thing, you nedd deserialize you JSON data. To do this using jQuery use the function parseJson that you can find here http://api.jquery.com/jquery.parsejson/ once you deserialized it, you can do whatever you want with this data since you manipulate it as a plain javascript array. Hope this helps.