Transforming an array in javascript

Question

I am new to javascript and am struggling to find an answer to this.

I have an object with a list of network interfaces and details. I guess this is an array of objects?:

> console.log(net);
[ { Interface: 'wlan0:',
    bytes: { Receive: '26087318', Transmit: '8475' },
    packets: { Receive: '379665', Transmit: '52' },
    errs: { Receive: '0', Transmit: '0' },
    drop: { Receive: '0', Transmit: '0' },
    fifo: { Receive: '0', Transmit: '0' },
    frame: { Receive: '0' },
    compressed: { Receive: '0', Transmit: '0' },
    multicast: { Receive: '0' },
    colls: { Transmit: '0' },
    carrier: { Transmit: '0' } },
  { Interface: 'lo:',
    bytes: { Receive: '228483', Transmit: '228483' },
    packets: { Receive: '4046', Transmit: '4046' },
    errs: { Receive: '0', Transmit: '0' },
    drop: { Receive: '0', Transmit: '0' },
    fifo: { Receive: '0', Transmit: '0' },
    frame: { Receive: '0' },
    compressed: { Receive: '0', Transmit: '0' },
    multicast: { Receive: '0' },
    colls: { Transmit: '0' },
    carrier: { Transmit: '0' } },
  { Interface: 'mon0:',
    bytes: { Receive: '285735889', Transmit: '0' },
    packets: { Receive: '1753373', Transmit: '0' },
    errs: { Receive: '0', Transmit: '0' },
    drop: { Receive: '1765559', Transmit: '0' },
    fifo: { Receive: '0', Transmit: '0' },
    frame: { Receive: '0' },
    compressed: { Receive: '0', Transmit: '0' },
    multicast: { Receive: '0' },
    colls: { Transmit: '0' },
    carrier: { Transmit: '0' } },
  { Interface: 'eth0:',
    bytes: { Receive: '6982603', Transmit: '22526425' },
    packets: { Receive: '58906', Transmit: '384822' },
    errs: { Receive: '0', Transmit: '0' },
    drop: { Receive: '0', Transmit: '0' },
    fifo: { Receive: '0', Transmit: '0' },
    frame: { Receive: '0' },
    compressed: { Receive: '0', Transmit: '0' },
    multicast: { Receive: '0' },
    colls: { Transmit: '0' },
    carrier: { Transmit: '0' } } ]

I want to transform into this result:

> console.log(result);
{ lo: 'lo',
  mon0: 'mon0',
  eth0: 'eth0',
  wlan0: 'wlan0' }

I have tried a few things in the node REPL console but I'm not getting anywhere:

> var result = {};
undefined
> Object.keys(net).forEach(function(ifname) {
... result[ifname] = ifname;
... });
undefined
> result
{ '0': '0', '1': '1', '2': '2', '3': '3' }

Another try:

> procfs.net(function(err,net){
... result = net.map(function(a) {return a.Interface;})
... });
undefined
> console.log(result);
[ 'wlan0:', 'lo:', 'mon0:', 'eth0:' ]
undefined

I can reference the data elements required individually, just struggling to put it all together:

> net[0].Interface
'wlan0:'
> net[1].Interface
'lo:'
> net[2].Interface
'mon0:'
> net[3].Interface
'eth0:'

Help appreciated!

zeppelin · Accepted Answer · 2016-11-12 10:15:07Z

1

EDIT: added the code to remove trailing colon character, to match the requested output format exactly

Just reduce it like that:

var result = net.reduce((ifaces,i) => { 
  var name = i.Interface.replace(/:$/,'');
  ifaces[name]=name; 
  return ifaces; 
},{})

Sample output

>>result
{ wlan0: "wlan0", lo: "lo", mon0: "mon0", eth0: "eth0" }

Alternatively, you can use Lodash (https://lodash.com/):

_.keyBy(net.map(i=>i.Interface.slice(0,-1)))

or some other utility library.

edited Nov 12, 2016 at 10:15

answered Nov 12, 2016 at 9:24

zeppelin

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Comments

Nina Scholz · Accepted Answer · 2016-11-12 09:16:51Z

You need to take the value from the Interface property and assign this value to the same key in the object.

var net = [{ Interface: 'wlan0:', bytes: { Receive: '26087318', Transmit: '8475' }, packets: { Receive: '379665', Transmit: '52' }, errs: { Receive: '0', Transmit: '0' }, drop: { Receive: '0', Transmit: '0' }, fifo: { Receive: '0', Transmit: '0' }, frame: { Receive: '0' }, compressed: { Receive: '0', Transmit: '0' }, multicast: { Receive: '0' }, colls: { Transmit: '0' }, carrier: { Transmit: '0' } }, { Interface: 'lo:', bytes: { Receive: '228483', Transmit: '228483' }, packets: { Receive: '4046', Transmit: '4046' }, errs: { Receive: '0', Transmit: '0' }, drop: { Receive: '0', Transmit: '0' }, fifo: { Receive: '0', Transmit: '0' }, frame: { Receive: '0' }, compressed: { Receive: '0', Transmit: '0' }, multicast: { Receive: '0' }, colls: { Transmit: '0' }, carrier: { Transmit: '0' } }, { Interface: 'mon0:', bytes: { Receive: '285735889', Transmit: '0' }, packets: { Receive: '1753373', Transmit: '0' }, errs: { Receive: '0', Transmit: '0' }, drop: { Receive: '1765559', Transmit: '0' }, fifo: { Receive: '0', Transmit: '0' }, frame: { Receive: '0' }, compressed: { Receive: '0', Transmit: '0' }, multicast: { Receive: '0' }, colls: { Transmit: '0' }, carrier: { Transmit: '0' } }, { Interface: 'eth0:', bytes: { Receive: '6982603', Transmit: '22526425' }, packets: { Receive: '58906', Transmit: '384822' }, errs: { Receive: '0', Transmit: '0' }, drop: { Receive: '0', Transmit: '0' }, fifo: { Receive: '0', Transmit: '0' }, frame: { Receive: '0' }, compressed: { Receive: '0', Transmit: '0' }, multicast: { Receive: '0' }, colls: { Transmit: '0' }, carrier: { Transmit: '0' } }],
    result = {};

net.forEach(function (o) {
    result[o.Interface] = o.Interface;
});

console.log(result);

Romain Lanz · Accepted Answer · 2016-11-12 09:34:18Z

This is a perfect example to use Array.reduce()!

net.reduce((interfaces, interface) => {
  interfaces[interface.Interface.slice(0, -1)] = interface.Interface.slice(0, -1)
  return interfaces
}, {})

const net = [{ Interface: 'wlan0:', bytes: { Receive: '26087318', Transmit: '8475' }, packets: { Receive: '379665', Transmit: '52' }, errs: { Receive: '0', Transmit: '0' }, drop: { Receive: '0', Transmit: '0' }, fifo: { Receive: '0', Transmit: '0' }, frame: { Receive: '0' }, compressed: { Receive: '0', Transmit: '0' }, multicast: { Receive: '0' }, colls: { Transmit: '0' }, carrier: { Transmit: '0' } }, { Interface: 'lo:', bytes: { Receive: '228483', Transmit: '228483' }, packets: { Receive: '4046', Transmit: '4046' }, errs: { Receive: '0', Transmit: '0' }, drop: { Receive: '0', Transmit: '0' }, fifo: { Receive: '0', Transmit: '0' }, frame: { Receive: '0' }, compressed: { Receive: '0', Transmit: '0' }, multicast: { Receive: '0' }, colls: { Transmit: '0' }, carrier: { Transmit: '0' } }, { Interface: 'mon0:', bytes: { Receive: '285735889', Transmit: '0' }, packets: { Receive: '1753373', Transmit: '0' }, errs: { Receive: '0', Transmit: '0' }, drop: { Receive: '1765559', Transmit: '0' }, fifo: { Receive: '0', Transmit: '0' }, frame: { Receive: '0' }, compressed: { Receive: '0', Transmit: '0' }, multicast: { Receive: '0' }, colls: { Transmit: '0' }, carrier: { Transmit: '0' } }, { Interface: 'eth0:', bytes: { Receive: '6982603', Transmit: '22526425' }, packets: { Receive: '58906', Transmit: '384822' }, errs: { Receive: '0', Transmit: '0' }, drop: { Receive: '0', Transmit: '0' }, fifo: { Receive: '0', Transmit: '0' }, frame: { Receive: '0' }, compressed: { Receive: '0', Transmit: '0' }, multicast: { Receive: '0' }, colls: { Transmit: '0' }, carrier: { Transmit: '0' } }]

const result = net.reduce((interfaces, interface) => {
  interfaces[interface.Interface.slice(0, -1)] = interface.Interface.slice(0, -1)
  return interfaces
}, {})

console.log(result)

This results in "["wlan0:", "lo:", "mon0:", "eth0:"]", not "{ lo: 'lo', mon0: 'mon0', eth0: 'eth0', wlan0: 'wlan0' }}", while that might work just as good (depending on further logic), that is still a different output.

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