presuppose

Assertion library

Syntax:

presuppose.validator(properties:object, options?:any, msg:string | ((propName:string) => string)):void;

Available validators are listed below

nonEmptyStrings

Checks if given object has only fields with non empty strings values. Example:

const presuppose = require(presuppose');

presuppose.nonEmptyStrings({ prop1: 'test', prop2: 'test2' });

the above code will not throw. However this:

presuppose.nonEmptyStrings({ prop1: 123, prop2: 'test2' });

will throw AssertionError because prop1 is not a stirng.

This assertion also checks for emptiness:

presuppose.nonEmptyStrings({ prop: '' });

will throw because prop is empty.

stringsOrUndefined

Checks if given object has only fields with strings or undefined values. Example:

presuppose.stringsOrUndefined({ prop1: 'abc', prop2: undefined });

the above code will not throw. However:

presuppose.stringsOrUndefined({ prop: 123 });

will throw AssertionError

arrays

Checks if given object has only fields with array valuest. Example:

presuppose.arrays({ arr: [] });

the above code will not throw. However:

presuppose.arrays({ arr: { length: 123 } });

will throw.

arraysOfNonEmptyStrings

Checks if given object has only fields with arrays of non empty strings as values.Example

presuppose.arraysOfNonEmptyStrings({ arr: [ 'item1', 'item2' ] });

the above code will not throw since the input object has only one key: arr which is an array of non empty strings. However:

presuppose.arraysOfNonEmptyStrings({ arr: [ 'item', 123 ] });

will throw.

specificValues

Checks if given object has only fields with values specified by an argument to this function. Example:

presuppose.specificValues({ prop1: 123, prop2: 123 }, 123);

will not throw. However:

presuppose.specificValues({ prop: 111 }, 123);

will throw;

objects

Checks if given object has only objects as fields. Example

presuppose.objects({ prop1: {foo: 'bar'}, prop2: new Date() });

will not throw. However this:

presuppose.objects({ prop1: 123 });

will throw. Also when given an array it will throw:

presuppose.objects({ prop1: [] }); // throws

stringsNotMatch

Checks if all properties in a given object do not match a certain pattern. Example:

presuppose.stringsNotMatch({ prop1: 'test' }, /error/);

the above code will not throw because 'test' do not match /error/. However:

presuppose.stringsNotMatch({ prop1: 'test' }, /te*/);

will throw.

numbers

Checks if all properties in a given object are numbers. Optionally can include range codnditions.

Example:

presuppose.numbers({prop1: '1'})

will throw, cause '1' is a string , while

presuppose.numbers({prop1: 1})

will not throw.

To check if the number is in specific range you can add a second parameter, which has to be an object containing one or more of the following props:

• greaterThan
• greaterThanOrEqual
• lessThan
• lesThanOrEqual

Example:

presuppose.numbers(
    {prop1:10},
    {greaterThan:5, lessThanOrEqual:10}
)

will not throw, as prop1 is greater than 5 and less than or equal 10.

Customizing error message

You can customize error message by providing a custom string:

presuppose.nonEmptyStrings({ a: 123 }, null, 'a cannot be empty');

If you have more then one property then it's useful to add a property name to the error message. you can do it like that:

presuppose.nonEmptyStrings({ a: 123, b: 222 }, null, propName => `${propName} cannot be empty`);

License

ISC - see LICENSE file