Utilizing the .map() function to retrieve an object from an array without a key

Exploring Dialogflow, I aim to retrieve the speech value for the object in the messages array that lacks a platform key:

"messages": [
    {
      "type": 0,
      "platform": "skype",
      "speech": "FOO"
    },
    {
      "type": 0,
      "platform": "line",
      "speech": "FOO"
    },
    {
      "type": 0,
      "platform": "facebook",
      "speech": "FOO"
    },
    {
      "type": 0,
      "platform": "telegram",
      "speech": "FOO"
    },
    {
      "type": 0,
      "platform": "kik",
      "speech": "FOO"
    },
    {
      "type": 0,
      "speech": "FOO"
    }
  ]

Currently, retrieving the value as follows:

messages = messages[messages.length - 1].speech;

However, relying on the last item being platform neutral is risky.

This was attempted:

 console.log(messages.filter(function(obj) {
    if (!(obj.hasOwnProperty('platform'))){
      return obj;
    }
  }));

An error occured 

TypeError: messages.map is not a function

How should the map function be adjusted for this scenario?

javascript

Answer №1

SOLUTION X:

If you're searching for specific content within messages, looping through them is a simple approach. Below is an example of how you can achieve this:

var messages =  [
    {
      "type": 0,
      "platform": "skype",
      "speech": "FOO"
    },
    {
      "type": 0,
      "platform": "line",
      "speech": "FOO"
    },
    {
      "type": 0,
      "platform": "facebook",
      "speech": "FOO"
    },
    {
      "type": 0,
      "platform": "telegram",
      "speech": "FOO"
    },
    {
      "type": 0,
      "platform": "kik",
      "speech": "FOO"
    },
    {
      "type": 0,
      "speech": "FOO"
    }
  ]
  for(var obj in messages){
    if(!(messages[obj].hasOwnProperty('platform'))){
        alert(messages[obj].speech);
    }
}

SOLUTION Y:

An alternative method to filter and map the data simultaneously can be used for more complex operations. The code snippet below demonstrates how it can be done:

var messages =  [
    {
      "type": 0,
      "platform": "skype",
      "speech": "FOO"
    },
    {
      "type": 0,
      "platform": "line",
      "speech": "FOO"
    },
    {
      "type": 0,
      "platform": "facebook",
      "speech": "FOO"
    },
    {
      "type": 0,
      "platform": "telegram",
      "speech": "FOO"
    },
    {
      "type": 0,
      "platform": "kik",
      "speech": "FOO"
    },
    {
      "type": 0,
      "speech": "FOO"
    }
  ]
  var result = messages.filter(function(obj){
    if (!(obj.hasOwnProperty('platform'))){
      return obj;
    }
}).map(m => m.speech);

alert(result);

Answer №2

After reviewing the code snippet provided, it seems like you may be attempting to use the map function on a Map/Associative Array (or JS object) which is not compatible with the map method. I have modified the sample code below to address this issue and provide a solution that should work for your scenario.

let messageMap = {"messages": [
    {
      "type": 0,
      "platform": "skype",
      "speech": "FOO"
    },
    {
      "type": 0,
      "platform": "line",
      "speech": "FOO"
    },
    {
      "type": 0,
      "platform": "facebook",
      "speech": "FOO"
    },
    {
      "type": 0,
      "platform": "telegram",
      "speech": "FOO"
    },
    {
      "type": 0,
      "platform": "kik",
      "speech": "FOO"
    },
    {
      "type": 0,
      "speech": "FOO"
    }
  ]};
  
  // Filter out messages without a platform defined.
  let platformlessMessages = messageMap['messages'].filter((message) => {
  
    return message.platform === undefined;
  });
  
  console.log(platformlessMessages);

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