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Isomorphic validation javascript library ISOMORPHIC-VALIDATION

Predicate().changed() method

Adds state callbacks which will be invoked after the predicate function execution if its current return value differs from the previous one.

Syntax

Predicate().changed(callback1, callback2, /* ..., */ callbackN)

Parameters

  • callback1, ..., callbackN
    Functions to add. The callback functions will be called with the following arguments:

Return value

The Predicate object.

Exceptions

If anything other than a function is passed in the corresponding error will be thrown.

Description

Adds state callbacks to the Predicate object. Once the Predicate in the specified state, the corresponding callbacks will be invoked one by one in the order they were added. The main purpose of state callbacks is to perform side effects related to the state. A ValidationResult object is passed into state callbacks.

Examples

import { Validation, Predicate } from "isomorphic-validation";


const { log } = console;
const logFn = (fn) => (value) => (log(`${fn.name}("${value}")`), fn(value));


// predicate functions
const hasLetterA = (value) => /[Aa]+/.test(value);
const hasLetterB = (value) => /[Bb]+/.test(value);
const hasLetterC = (value) => /[Cc]+/.test(value);


// state callbacks
const startedCB = ({ isValid }) => {
    log(`startedCB({ isValid: ${isValid} }) <-- before`);
};


const validCB = ({ isValid }) => {
    log(`validCB({ isValid: ${isValid} }) <-- after`);
};


const invalidCB = ({ isValid }) => {
    log(`invalidCB({ isValid: ${isValid} }) <-- after`);
};


const changedCB = ({ isValid }) => {
    log(`changedCB({ isValid: ${isValid} }) <-- changes`);
};


const validatableObject = { value: '' };


const v = Validation(validatableObject)
    .constraint( logFn(hasLetterA) )
    .constraint( logFn(hasLetterB) )
    .constraint(
        Predicate( logFn(hasLetterC) )
            .started(startedCB)     // adding state callbacks
            .valid(validCB)         // adding state callbacks
            .invalid(invalidCB)     // adding state callbacks
            .changed(changedCB)     // adding state callbacks
    )
    .started(() => log('---'));


validatableObject.value = 'A';
await v.validate(); // hasLetterC() -> false


validatableObject.value = 'Abc';
await v.validate(); // hasLetterC() -> true, changedCB will be called


validatableObject.value = 'ABCabc';
await v.validate(); // hasLetterC() -> true


validatableObject.value = 'ABab';
await v.validate(); // hasLetterC() -> false, changedCB will be called


// Output:
// ---
// hasLetterA("A")
// hasLetterB("A")
// startedCB({ isValid: false }) <-- before
// hasLetterC("A")
// invalidCB({ isValid: false }) <-- after
// ---
// hasLetterA("Abc")
// hasLetterB("Abc")
// startedCB({ isValid: false }) <-- before
// hasLetterC("Abc")
// changedCB({ isValid: true }) <-- changes
// validCB({ isValid: true }) <-- after
// ---
// hasLetterA("ABCabc")
// hasLetterB("ABCabc")
// startedCB({ isValid: true }) <-- before
// hasLetterC("ABCabc")
// validCB({ isValid: true }) <-- after
// ---
// hasLetterA("ABab")
// hasLetterB("ABab")
// startedCB({ isValid: true }) <-- before
// hasLetterC("ABab")
// changedCB({ isValid: false }) <-- changes
// invalidCB({ isValid: false }) <-- after