Composers

Comparators

Comparators are used for validation and conditional display. The comparator operations are composed into a single function that does the potentially-nested comparison (with and and or):

const composeComparators = operation => (arg? => Either<Array<Error>, result>)

Examples of comparator operations are IsMoreThan, IsAfterAlphabetically, IsBeforeDateTime, Matches, and IsDisjointSet.

If the comparison evaluates to false, then a Left is returned with one or more Error objects explaining which comparison(s) failed.

If the comparison evaluates to true, then a Right is returned with the value that was tested. See composeComparators for more detail.

Operators

Operators are used for numerical calculations. Not only can these operations be nested to any depth, but they can be used to generate the operand and/or test values for use in comparator operations.

const composeOperators = operation => (arg? => Either<Array<Error>, result>)

Operators include the JavaScript arithmetic operators and the Math module operations. Examples: add, subtract, multiply, divide, floor, mean, and root. See the full list of operators.

If the operation fails, then a Left is returned with one or more Error objects explaining which comparison(s) failed. If the operations succeeds, then a Right is returned containing the calculated value (a number). This result can be used in other calculations, comparisons, etc.

Validation

The composeValidation function wraps the composeComparators function, returning the same results. In the future, there may be added functionality here.

const composeValidator = operation => (arg? => Either<Array<Error>, result>)

Conditionals

The composeConditional function wraps the composeComparators function, but returns a plain Boolean value, true or false.

const composeConditional = operation => (arg? => Boolean)

This makes it easy to use the composeComparators function for conditional display by returning a plain Boolean instead of an Either.