Question

I have a Javascript object and I’m struggling mightly to check in a loop if postsome is undefined.

Here is my object:

var indices = [{
    "indexAB": [{
        "postsome": [
            "keyword_abc",
            "keyword_def"
         ]
       }]
    },{
    "indexA": [{
        "postsome": [
            "keyword_abc"
        ]
      }]
    }
 ]

Problem is, I can’t reference indexA,indexAB or postsome directly. All will be variables. This is what I’m trying:

// passed parameter
var doc._id = "postsome";

// mapping priv
// "indices": [
//    {"name":"indexA","fields":["findMeA"]},
//    {"name":"indexAB", "fields":["findMeA","findMeB"]}
//    ],

for (var i = 0, l = indices.length; i < l; i += 1) {

  var index = priv.indices[i];
      index_name = index["name"]; // indexAB or indexA

  // I can't reference indexAB directly 
  if ( indices[i].indexAB !== undefined && indices[i].indexAB.length  >  0 )          {
      console.log( indices[i].indexAB );
      console.log( indices[i].indexAB[0][doc._id] );

      if (indices[i].indexAB[0][doc._id] !== undefined) {
        console.log("gotcha");
        trigger = true;
      }
    }
}

So when I use indexAB hardcoded it works, but I need to loop through the values (‘indexA’ and ‘indexAB’ instea).

Question:
Is there any way to replace .indexAB[0] with a variable? If so, how?

Thanks!

Answer 1

Just use bracket notation, the exact same way you do with [doc._id].

if (indices[i][index_name] !== undefined && indices[i][index_name].length > 0)

Bracket notation and dot notation are interchangable, so these two lines are equivalent:

indices.foo
indices["foo"]

If you need to use a variable, however, indices.varName would translate to indices["varName"], so you must use bracket notation to ensure that it uses the variable value instead of the variable name as a string.