sliceByValue

sliceByValue.test.ts

import { sliceByValue } from './sliceByValue';

const array = [false, false, true, false, false, false];

describe('sliceByValue', () => {
  it('should slice by a boolean type value', () => {
    expect(sliceByValue(array, true)).toEqual([false, false, false]);
  });

  it('should slice by a boolean type value when its the last element', () => {
    expect(sliceByValue(array, false)).toEqual([]);
  });

  it('should not modify array when an index does not exist', () => {
    const testArray = [...array, 'hi'];

    expect(sliceByValue(testArray, 'some value')).toEqual(testArray);
  });
});

sliceByValue.ts

/**
 * This function slies array by a value
 * ([false, true, false], true) => [false]
 */
export const sliceByValue = <T>(array: T[], value: T) => {
  const initialArray = [...array];

  const index = initialArray.lastIndexOf(value);

  if (index === -1) {
    return initialArray;
  }

  return initialArray.slice(index + 1);
};