Remove from string chars at indexes

removeCharsAtIndexes.ts

export function removeCharsAtIndexes(inputString:string, indexes:number[]):string {
  return indexes.reduce((sourceString:string, indexToRemove:number, currentIndex:number) => {
    return sourceString.slice(0, indexToRemove - currentIndex) + sourceString.slice(indexToRemove - currentIndex + 1);
  }, inputString);
}

test.ts

describe('removeCharsAtIndexes', () => {
  describe('removes characters from the given string according to an array containing indexes to be removed,' +
    'assuming that the given indexes are sorted', () => {
    [
      {
        input: 'some string',
        indexes: [1, 2, 3],
        caseName: 'subsequent chars from the middle of the string',
        expectedOutput: 's string'
      },
      {
        input: 'some string',
        indexes: [0],
        caseName: 'char at the beginning of the string',
        expectedOutput: 'ome string'
      },
      {
        input: 'some string',
        indexes: [10],
        caseName: 'char at the end of the string',
        expectedOutput: 'some strin'
      },
      {
        input: 'some string',
        indexes: [0, 7, 10, 11, 15, 18],
        caseName: 'chars even if there are extra indexes in the given array',
        expectedOutput: 'ome stin'
      }
    ].forEach((stringCase) => {
      it(`correctly removes ${stringCase.caseName}`, () => {
        removeCharsAtIndexes(stringCase.input, stringCase.indexes).should.equal(stringCase.expectedOutput);
      });
    });
  });
});