findIndex Array method in TypeScript

Question

I'm very new to Angular 4 development. I encounter someArray.findIndex() is not a function. How to add this .findIndex() javascript function in TypeScript.

I'm building a calendar component, following function gives me error

WEBPACK_IMPORTED_MODULE_2_lodash.findIndex is not a function at CalendarComponent.isSelected (calendar.component.ts:4

isSelected(date: moment.Moment): boolean {
    return _.findIndex(this.selectedDates, (selectedDate) => {
      return moment(date).isSame(selectedDate.mDate, 'day');
    }) > -1;
  }

Thank you so much.

Aluan Haddad · Accepted Answer · 2018-07-29 17:11:06Z

5

It's not about Typescript. Javascript functions are included in Typescript. You are trying to use Lodash function. Make sure that you installed and imported it on top of the file:

import _ from 'lodash';

or just use Javascript function:

isSelected(date: moment.Moment): boolean {
    return this.selectedDates.findIndex((selectedDate) => {
      return moment(date).isSame(selectedDate.mDate, 'day');
    });
}

edited Jul 29, 2018 at 17:11

Aluan Haddad

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answered Mar 27, 2018 at 5:33

Patryk Gułaś

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1 Comment

Vishwa Over a year ago

Thank you so much for your answer. This solved my problem. I've missed to install the lodash module.

david valentino · Accepted Answer · 2018-03-27 07:52:40Z

1

you can use indexOf

[1,2,3,4,5].indexOf(1) //return 0
[1,2,3,4,5].indexOf(5) //return 4
[1,2,3,4,5].indexOf(6) //return -1
[1,2,3,4,5].indexOf(0) //return -1

answered Mar 27, 2018 at 7:52

david valentino

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Comments

Mohammad Usman · Accepted Answer · 2018-07-29 17:06:52Z

1

selectedDate = arrayName.find(item => item.date === searchingdate);

edited Jul 29, 2018 at 17:06

Mohammad Usman

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answered Mar 27, 2018 at 5:45

Sarath Kumar

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Comments

Aluan Haddad · Accepted Answer · 2018-07-29 17:10:51Z

1

You are calling findIndex method of _. You are either using UnderscoreJS or Lodash.

As the error says WEBPACK_IMPORTED_MODULE_2_lodash.findIndex is not a function It means you are using lodash.

Import lodash library and it will work.

import _ from 'lodash';

edited Jul 29, 2018 at 17:10

Aluan Haddad

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answered Mar 27, 2018 at 5:44

Laxmikant Dange

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