JavaScript: How to filter data in an array

Question

I have following object in JS:

[
  {
    "financial_year":1,
    "mainline_revenue":18743.0,
    "regional_revenue":2914.0,
    "other_revenue":3198.0,
    "non_operating_items":-1983.0
  },
  {
    "financial_year":2,
    "mainline_revenue":20218.0,
    "regional_revenue":3131.0,
    "other_revenue":3394.0,
    "non_operating_items":-3233.0
  },
  {
    "financial_year":3,
    "mainline_revenue":30802.0,
    "regional_revenue":6322.0,
    "other_revenue":5526.0,
    "non_operating_items":-1367.0
  }
]

financial_year is the unique identifier which I want to use to filter data. How can I filter data where for example financial_year is 2 and put the other values in an array?

Answer 1

You can use the filter method on arrays. filter takes a callback which returns true or false (more accurately, a truthy or falsey value). If it returns true, that object is included in the resulting array.

let input = [
  {
    "financial_year":1,
    "mainline_revenue":18743.0,
    "regional_revenue":2914.0,
    "other_revenue":3198.0,
    "non_operating_items":-1983.0
  },
  {
    "financial_year":2,
    "mainline_revenue":20218.0,
    "regional_revenue":3131.0,
    "other_revenue":3394.0,
    "non_operating_items":-3233.0
  },
  {
    "financial_year":3,
    "mainline_revenue":30802.0,
    "regional_revenue":6322.0,
    "other_revenue":5526.0,
    "non_operating_items":-1367.0
  }
];
let output = input.filter((obj) => obj.financial_year !== 2);
console.log(JSON.stringify(output, null, 2));

Or rewritten with ES5:

var input = [
  {
    "financial_year":1,
    "mainline_revenue":18743.0,
    "regional_revenue":2914.0,
    "other_revenue":3198.0,
    "non_operating_items":-1983.0
  },
  {
    "financial_year":2,
    "mainline_revenue":20218.0,
    "regional_revenue":3131.0,
    "other_revenue":3394.0,
    "non_operating_items":-3233.0
  },
  {
    "financial_year":3,
    "mainline_revenue":30802.0,
    "regional_revenue":6322.0,
    "other_revenue":5526.0,
    "non_operating_items":-1367.0
  }
];
var output = input.filter(function(obj) {
  return obj.financial_year !== 2;
});
console.log(JSON.stringify(output, null, 2));