Replace javascript array with item inside of object

Question

I want to show some data depending on which month it is. I have an array from 0 to 11. I'm confused on how to do this because there are multiple arrays inside of the object and it's scaring me lol

[
  {
    l: false,
    u: 'AU',
    n: 'Adelaide',
    rain: [
      22.4091,
      18,
      26.0909,
      42.875,
      56.9205,
      68.0568,
      75.4205,
      66.3636,
      58.8977,
      48.75,
      28.2159,
      27.9545,
    ],
  },
  {
    l: false,
    u: 'AU',
    n: 'A Different Place',
    rain: [
      22.4091,
      18,
      26.0909,
      42.875,
      56.9205,
      68.0568,
      75.4205,
      66.3636,
      58.8977,
      48.75,
      28.2159,
      27.9545,
    ],
  },
];

I have a variable that I can reference like this: getMonth(new Date(this.props.startDate))

0

Can I do something like this?

forEach(data[x].rain[getMonth(new Date(this.props.startDate))])

I'd like to replace the existing rain array with the data of the corresponding month. So for example if it was January (0) I'd like data[1].rain = 22.4091

expected output if (getMonth = 0):

[
  {
    l: false,
    u: 'AU',
    n: 'Adelaide',
    rain: 22.4091
  },
  {
    l: false,
    u: 'AU',
    n: 'A Different Place',
    rain: 22.4091
    ],
  },
];

What do you want the output to be? It's confusing at the moment — Jack Bashford
– Jack Bashford, Commented May 27, 2019 at 14:34
to replace the array with the integer which is an index of month — jaksco
– jaksco, Commented May 27, 2019 at 14:38
if value will change based on month, you can't put 0, see below answer — Muthu R
– Muthu R, Commented May 27, 2019 at 14:51

Maheer Ali · Accepted Answer · 2019-05-27 14:40:30Z

1

You can use map(). Return an object from map() with all properties same as previous but change rain to the the first element of it.

 let arr = [ { l: false, u: 'AU', n: 'Adelaide', rain: [ 22.4091, 18, 26.0909, 42.875, 56.9205, 68.0568, 75.4205, 66.3636, 58.8977, 48.75, 28.2159, 27.9545, ], }, { l: false, u: 'AU', n: 'A Different Place', rain: [ 22.4091, 18, 26.0909, 42.875, 56.9205, 68.0568, 75.4205, 66.3636, 58.8977, 48.75, 28.2159, 27.9545, ], }, ];

const res = arr.map(x => ({...x,rain:x.rain[0]}))
console.log(res)

answered May 27, 2019 at 14:40

Maheer Ali

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2 Comments

jaksco Over a year ago

so I just put [getMonth(new Date(this.props.startDate))] instead of [0]?

Maheer Ali Over a year ago

@jaksco Yes try that and tell me if it works or not.

Muthu R · Accepted Answer · 2019-05-27 14:46:39Z

0

you can do this

let data = [ { l: false, u: 'AU', n: 'Adelaide', rain: [ 22.4091, 18, 26.0909, 42.875, 56.9205, 68.0568, 75.4205, 66.3636, 58.8977, 48.75, 28.2159, 27.9545, ], }, { l: false, u: 'AU', n: 'A Different Place', rain: [ 22.4091, 18, 26.0909, 42.875, 56.9205, 68.0568, 75.4205, 66.3636, 58.8977, 48.75, 28.2159, 27.9545, ], }, ];

const res = data.map(x => ({...x,rain:x.rain[ (new Date(this.props.startDate).getMonth()) ]}))
console.log(res)

if this is already date then this.props.startDate.getMonth() else convert as above

answered May 27, 2019 at 14:46

Muthu R

8061 gold badge10 silver badges15 bronze badges

2 Comments

jaksco Over a year ago

cool. is there a difference in memory between .getMonth() and the way I was doing it? yours is working. I guess that means I don't need to import getMonth?

Muthu R Over a year ago

getMonth is default function of date in javascript, no need any imports

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