Loop through object within an array in javascript

Question

I want to iterate through this array so I can print all the topic_name within the array.

a = [
 {
 "topic_name": "abc",
 "rdf_id": "pyt1.1",
 "ex_name": "hello_world",
 "line_number": "1",
 "code": "some code",
 "comment": "some comment"
 },
 {
  "topic_name": "abc",
  "rdf_id": "pyt1.2",
  "ex_name": "hello_world",
  "line_number": "2",
  "code": "some code",
  "comment": "some comment"
  },
]

i have tried the following...but no help

for(var i = 0; i < a.length; i++) {
  var item_name = a[i];
  var arr = item_name.topic_name;
  console.log(arr);
}

Do you? And how far did you get towards achieving this goal? Where did you get stuck? What went wrong? — David Thomas, Dec 08 '15 at 04:21
You want to [`map`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/map) over the array? `input.map(function (x) { return x.topic_name; })` — Chris Martin, Dec 08 '15 at 04:22
@Hunan: that's fine by me, I have no particular axe to grind with those trying to help; I'd just prefer that the question being answered was worth an answer. ...which possibly sounds quite mean. — David Thomas, Dec 08 '15 at 04:24
You're trying to parse a String as a float, so your `iP` becomes `NaN`. What are you trying to do? — Hunan Rostomyan, Dec 08 '15 at 04:39
sorry that was my bad...i have updated the code that i tried...it gives me undefined...could you check it? — Hardik Vasa, Dec 08 '15 at 04:49

score 1 · Accepted Answer · answered Dec 08 '15 at 04:21

1

You can try something like this:

arr.map(function(item) {
  return item.topic_name;
});
//=> ["abc", "abc"]

answered Dec 08 '15 at 04:21

Hunan Rostomyan

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1

Would be better to teach the for-loop before `map`. – Dec 08 '15 at 04:25

Loop through object within an array in javascript

1 Answers1