Why do I have to use "tracks" like this not like this tracks?

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JavaScript

var recordCollection = {
  2548: {
    albumTitle: 'Slippery When Wet',
    artist: 'Bon Jovi',
    tracks: ['Let It Rock', 'You Give Love a Bad Name']
  },
  2468: {
    albumTitle: '1999',
    artist: 'Prince',
    tracks: ['1999', 'Little Red Corvette']
  },
  1245: {
    artist: 'Robert Palmer',
    tracks: []
  },
  5439: {
    albumTitle: 'ABBA Gold'
  }
};

// Only change code below this line
function updateRecords(records, id, prop, value) {
  if (prop!= 'tracks' && value!='') {
    records[id][prop]=value;
  }else if (prop==='tracks' &&records[id].hasOwnProperty('tracks')===false) {
    record[id][prop]=[value];
  }else if(prop==='tracks' &&value!="") {
    records[id][prop].push(value);
  }else if(value==="") {
    delete records[id][prop];
  }
return records
  
}

in recordCollection object tracks is a array containing string.

What I have tried:

i tried using tracks instead of using "tracks" an thus a eror came that tracks is undefined

Posted 19-May-21 8:04am

Aurangajeb Azad

Updated 19-May-21 8:45am

PIEBALDconsult

v2

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Wendelius · Answer 1 · 2021-05-19T08:45:00

Solution 1

Because the prop parameter contains the name of the property at hand and the name is a string. This is why you need to compare it to another string (literal in this case).

Posted 19-May-21 8:45am

Wendelius

Comments

Aurangajeb Azad 24-May-21 6:00am

but tracks is already declared in the object

Wendelius 24-May-21 10:47am

It's a value of an object, not an object by itself. So you cannot reference tracks alone without specifying the object. However, you can investigate if the property is named tracks

Aurangajeb Azad 4-Jun-21 5:25am

could you give an example?

Wendelius 4-Jun-21 5:29am

You already have an example in your code. The line

if (prop!= 'tracks'...

checks if the property is named 'tracks' or not.

If you mean how the names are found out, there are multiple ways and situations, but have a look at for example Object.getOwnPropertyNames() - JavaScript | MDN[^]