Cannot get properties of javascript object

Question

I have a for loop that adds properties to the data object

words is an array of strings

for (let i = 0; i < words.length; i++) {
  let word = words[i];
  data[word] = i;
}

After that, my objext looks like this:

data = {"the": 0, "of": 1, "and": 2, "to": 3, "a": 4, …};

I have tried

data['the'];

but it returns undefined

How do I retrieve the value of the property?

Here is my full code

let vocab = {};

$.ajax({
  url: "10000words.txt",
  success: function(data) {
    data = data.split(/\n/).slice(0, 10000);
    for (let i = 0; i < data.length; i++) {
      let word = data[i];
      vocab[word] = i;
    }
    console.log(vocab['test']);
  }
});

When I type vocab into the console, it prints out vocab but when I try vocab['the'] it returns undefined

`data['the']` works fine. You're doing something else wrong. Please provide an https://stackoverflow.com/help/mcve — SLaks, Jul 19 '18 at 23:33
You wouldn't be trying to do this in an async callback like a http request, would you? — Mark, Jul 19 '18 at 23:34
@Mark Meyer I add to the data object with an http request then I try `data['the']` but it is still undefined — bakely, Jul 19 '18 at 23:37
if you do:`var data = { "the": 0, "of": 1, "and": 2, "to": 3, "a": 4}; var result = data['the'];` you will see that it works fine. Maybe you miss some variable initialisation or something else. — Marlon Assef, Jul 19 '18 at 23:40
@bena The question was whether you’re trying to _access_ `vocab` outside the `success` callback, not whether you’ve declared it outside. Your issue is impossible to reproduce, if you didn’t actually access `vocab` outside of `success`. That’s why I think the most likely issue is this: [Why is my variable unaltered after I modify it inside of a function? - Asynchronous code reference](https://stackoverflow.com/questions/23667086/why-is-my-variable-unaltered-after-i-modify-it-inside-of-a-function-asynchron) — Sebastian Simon, Jul 19 '18 at 23:45
@Kaiido Read the edited comment. It’s just the most likely scenario. — Sebastian Simon, Jul 19 '18 at 23:47
@bena The question is either a duplicate, or it’s caused by a typo. Again, the issue is impossible to be reproduced with the code you’ve shown. Try using `debugger`, try logging `vocab` by itself. — Sebastian Simon, Jul 19 '18 at 23:50
@bena Actually… try `console.log([...Object.keys(vocab).find((word) => /t[^a-z]*h[^a-z]*e/.test(word))]);` and see whether it matches `["t", "h", "e"]`. There may be invisible characters within your words, thus `vocab.the` won’t work. — Sebastian Simon, Jul 20 '18 at 00:17

score 1 · Answer 1 · answered Jul 19 '18 at 23:33

Here is an example of how to get a value by the object key.

const words = ['Hello', 'world'];
const data = {};

for(let i = 0; i < words.length; i++) {
  const word = words[i];
  data[word] = i;
}

const index = data['Hello'];

document.write(index);

Cannot get properties of javascript object

1 Answers1