Getting index of first object in an array that has "name" property starting with selected letter

Question

I have alphabetically ordered list of countries in an array like following:

[
  {
    name: "United States",
    country_code: "US",
    dial_code: "+1"
  },
  { .. etc }
]

I am listening for users key input and lets say they press "a" key. I want to get index of first object in the array where name starts with "a".

Now my question is not to how to perform this whole operation, just advice / ideas on how to find such index in the array if I already know user pressed "a". I was looking into lodash to do this, but wasn't able to figure it out, hence feel free to use third party libraries if they are appropriate to solve this.

stasovlas · Accepted Answer · 2016-11-28 07:23:27Z

1

use _.findIndex to find first matched item index:

var firstIndex = _.findIndex(countries, function(country) {
    return _.chain(country)
        .get('name', '')
        .lowerCase()
        .startsWith('a')
        .value();
});

edited Nov 28, 2016 at 7:23

answered Nov 28, 2016 at 2:03

stasovlas

7,4362 gold badges30 silver badges30 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Nina Scholz · Accepted Answer · 2016-11-27 21:42:27Z

You could use an object with the first letter and an index for the access to the given array and end of the array with the same letter, like

var abc = {
    u: [0, 1]
}

Example with letter 'u':

var countries = [{ name: "United Kingdom", country_code: "UK", dial_code: "+44" }, { name: "United States", country_code: "US", dial_code: "+1" }, { name: "France", country_code: "FR", dial_code: "+33" }, { name: "Italy", country_code: "IT", dial_code: "+16" }],
    abc = Object.create(null);

countries.sort(function (a, b) {
    return a.name.localeCompare(b.name);
});

countries.forEach(function (a, i) {
    var c = a.name[0].toLowerCase();
    if (!abc[c]) {
        abc[c] = [i];
    }
    abc[c][1] = i + 1;
});

console.log(Array.prototype.slice.apply(countries, abc['u']));
console.log(abc);

.as-console-wrapper { max-height: 100% !important; top: 0; }

kevin ternet · Accepted Answer · 2016-11-27 21:09:13Z

0

You could implement a function that would filter countries which name start with the letter given as parameter :

var countries = [
  {
    name: "United States",
    country_code: "US",
    dial_code: "+1"
  },
  {   name: "France",
    country_code: "FR",
    dial_code: "+33"
  },
  {   name: "Italy",
    country_code: "IT",
    dial_code: "+16"
  }
]
var selectedCountries = (array, letter) => array.filter(x => x.name.indexOf(letter) === 0);

console.log(selectedCountries(countries, "F"));

answered Nov 27, 2016 at 21:09

kevin ternet

4,6322 gold badges21 silver badges27 bronze badges

Comments

adeneo · Accepted Answer · 2016-11-27 21:16:22Z

0

If older browsers aren't an issue, you can combine Array.find and String.startsWith

var obj = arr.find( x => x.name.startsWith('a'));

answered Nov 27, 2016 at 21:16

adeneo

319k29 gold badges410 silver badges392 bronze badges

Collectives™ on Stack Overflow

Getting index of first object in an array that has "name" property starting with selected letter

4 Answers 4

Comments

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related