How to append an object to a Javascript JSON object

Question

I have a javascript object, which contains JSON in the form of an array of objects, such as:

columnDefs: [
  { name: 'Report', field: 'RPT', width: 80 },
  { name: 'Element', field: 'ELEM', width: 200 },
  ...
]

I need to add

cellClass: myFunction

to each individual column def in the columnDefs array of objects, so it is like:

columnDefs: [
  { name: 'Report', field: 'RPT', width: 80, cellClass: myFunction },
  { name: 'Element', field: 'ELEM', width: 200, cellClass: myFunction  },
  ...
]

Note that myFunction should not be encased in quotes. Since each column def is an object, and not an array, I understand that I need to convert it to an array before I can add anything to it:

var keys = Object.keys( columnDefs );
for( var key in keys ) {
  var col = columnDefs[key]
  var colArray = [];
  colArray.push( JSON.parse( JSON.stringify( col )));
  colArray.push( { cellClass: myFunction } );
  colDefs[key] = colArray;
}

However the above code generates the following which is not what is needed:

[    { name: 'Report', field: 'RPT', width: 80 },  { cellClass: myFunction } ]

There must be an easier and better way to do this?

jcubic · Accepted Answer · 2016-02-01 16:20:56Z

3

Try:

columnDefs.forEach(function(obj) {
   obj.cellClass = myFunction;
});

answered Feb 1, 2016 at 16:20

jcubic

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Comments

Ven · Accepted Answer · 2016-02-01 16:20:40Z

2

You might be misguided about what in does: it already iterates the key of an object (or the indexes of an array).

What you want instead is to parse your json string once, alter it in a loop, then re-serialize it:

var json = "...."; // your json input
var columnDefs = JSON.parse(json);
for (var i in columnDefs) { // columnDefs is an array, i the index
  var row = columnDefs[i];  // index into columnDefs to get the object
  row.cellClass = myFn(row);
}
var newJson = JSON.stringify(columnDefs); // your json output – skip this step if not needed

answered Feb 1, 2016 at 16:20

Ven

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Comments

NMunro · Accepted Answer · 2016-02-01 16:22:02Z

0

Is map what you need? Map returns a new array based on transforming the old one.

var arr = [
  { name: 'Report', field: 'RPT', width: 80 },
  { name: 'Element', field: 'ELEM', width: 200 }
].map(function(element) {
  element.cellClass = myFunction;
  return element;
});

answered Feb 1, 2016 at 16:22

NMunro

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Comments

shershen · Accepted Answer · 2016-02-01 16:27:56Z

0

var keys = Object.keys( columnDefs );
keys.forEach(function(item){
  var col = columnDefs[item]
  col['cellClass'] = myFunction
}

edited Feb 1, 2016 at 16:27

answered Feb 1, 2016 at 16:20

shershen

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2 Comments

Ven Over a year ago

There's no reason to use Object.keys here, is there?

jcubic Over a year ago

Every one in colDefs[key] = colArray; is undefined

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