Typescript: How to get boolean value from cell?

[DavidPx]

If I'm writing a Typescript helper function like this:

const GetBooleanFromCell = (cell: Excel.Cell) : boolean => {
    if (cell.type === Excel.ValueType.Boolean) {
        // Error Type 'CellValue' is not assignable to type 'boolean'
        return cell.value;
    }
    return false;
}

How can I test for boolean content and then return it? While debugging I do see that .value is indeed a boolean... but how do I tell my Typescript compiler this fact?

Thank you!

[DavidPx]

This approach seems to work, testing the value against true. Not sure if it's the best solution, though.

const GetBooleanFromCell = (cell: Excel.Cell) : boolean => {
    if (cell.type === Excel.ValueType.Boolean) {
        return cell.value === true;
    }
    return false;
}

[Siemienik]

I usually use this mapper

https://github.com/Siemienik/XToolset/blob/master/packages/xlsx-import/src/mappers/booleanMapper.ts#L2-L3

export const booleanMapper: ValueMapper<boolean> = value => Boolean(Number.parseFloat(value));

Unit test, which shows what values are mapped into: https://github.com/Siemienik/XToolset/blob/master/packages/xlsx-import/tests/unit/mappers/booleanMapper.test.ts#L7-L20

            { inValue: null, expectedResult: false },
            { inValue: '', expectedResult: false },
            { inValue: '  ', expectedResult: false },
            { inValue: '0', expectedResult: false },
            { inValue: '000', expectedResult: false },
            { inValue: 'true', expectedResult: false },
            { inValue: 'false', expectedResult: false },
            { inValue: 'a0.1', expectedResult: false },

            { inValue: '001', expectedResult: true },
            { inValue: '123', expectedResult: true },
            { inValue: '0.1', expectedResult: true },
            { inValue: '-1', expectedResult: true },
            { inValue: '   -1.2123asd', expectedResult: true },

[skypesky]

A

    const GetBooleanFromCell = (cell: Cell): boolean => {
      if (typeof cell.value === 'boolean') {
        return cell.value;
      }
      return false;
    }

B

    const GetBooleanFromCell = (cell: Cell): boolean => {
      if (cell.type === ValueType.Boolean) {
        return cell.value as boolean;
      }
      return false;
    }