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Custom validators

validator property

You can create completely custom validators using the validator property. If the provided function returns a falsey value, like false, null, undefined, "" or 0, then that means that the validator pased, and an error won't be returned. If it returns any other value, then it means there's an error, and the validator error function will be executed. The first parameter of the error function will always be the value that got received, the second will be the value returned by the validator, and the third one is the path to the property.

const validator = Builder.schema({
    name: Builder.string()
        .validator(str => str.startsWith("--"))
        .err("validator", () => "The string cannot start with '--'")
});

const validator = {
    properties: {
        name: {
            type: "string",
            validator: str => str.startsWith("--"),
            errors: {
                validator: () => "The string cannot start with '--'"
            }
        }
    }
}

Custom arguments

Since objvl compiles the schema into a function, you cannot use any variables inside the validator and error functions. To fix this, you can pass custom argument names in the compile function.

const validator = compile({...}, "arg1", "arg2");

And then call the validator like this:

const valueOutsideValidator = 42;
validator({...}, "Hello World", valueOutsideValidator);

Now the functions inside the validator can use the arguments arg1 and the valueOutsideValidator variable! This creates another problem, though: If you're using an IDE, then it's going to complain that arg1 and arg2 are not defined. The only way to fix this is to pass the function as a string:

const validator = Builder.schema({
    name: Builder.string()
        .validator(str => str.startsWith("--"))
        .err("validator", "() => ({ code: errors.VALIDATOR })")
}, "errors");

const errors = { VALIDATOR: 1001 };
validator({...}, errors);

const validator = {
    properties: {
        name: {
            type: "string",
            validator: str => str.startsWith("--"),
            errors: {
                validator: () => "() => ({ code: errors.VALIDATOR })"
            }
        }
    }
}

const errors = { VALIDATOR: 1001 };
validator({...}, errors);