Rails Hash in javascript, access values

Question

I have a following javascript code:

<input type="hidden" name="query_form_select_ops" id="query_form_select_ops" value='<%= schema%>'  />

<script>
  function select_pk2(cell){
  var val = $('#query_form_opt_'+cell+'_1').val();
  var opts = $('#query_form_select_ops').val();  
  }
</script>

Example:

schema is a typical ruby hash:

{ 
  "car"=>{"col"=>"blue", "engine"=>"HHd4M"},
  "train"=>{"col"=>"black", "engine"=>"8495f"}
}

The variable val has a value "train" and opts the whole ruby hash

To access the col and engine of a train in ruby: schema["train"]. How can I do the same in javascript?
I have tried:

var select = opts[val]

but it tells me that var in undefined. How can I access the values of a ruby hash in javascript given a hash and one of the keys?

Krzysztof Rygielski · Accepted Answer · 2015-05-08 09:44:08Z

1

Dump schema hash as a json and then parse it back in javascript. Something like this:

<input type="hidden" name="query_form_select_ops" id="query_form_select_ops" value='<%= schema.to_json %>'  />

And script:

function select_pk2(cell){
  var val = $('#query_form_opt_'+cell+'_1').val();
  var opts = JSON.parse($('#query_form_select_ops').val());  
}

This way you should be able to access values in the way you want.

Each individual value of the hash in your example is hash as well, so you can access them by using proper keys. Like this:

opts['car']['col'];

edited May 8, 2015 at 9:44

answered May 8, 2015 at 9:30

Krzysztof Rygielski

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3 Comments

Anni Over a year ago

I did it but if I alert(opts[val]) I get [object Object]. alert(opts[val][0]) and alert(opts[val][1]) are undefined

Krzysztof Rygielski Over a year ago

And that's normal behavior, as you also have hashes as nested values. And hash (in this case - javascript object) mapped on string is "[object Object]". You can access individual properties of each value as well. Try console.log(opts[val]) and you should see the proper output on browser's dev console (on chrome or ff). If you want opts[val] back as a string (json). Just do JSON.stringify(opts[val]), and you should get the json as the alert output.

Krzysztof Rygielski Over a year ago

I've updated the answer. No wonder you get opts[val][0] as undefined, as there's no such key in any of the hash values. Do opts[val]['col'] for example.

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