JavaScript Callback Utilities: Fix Undefined Function Errors

These production-ready utility functions help you fix undefined is not a function error in JavaScript callbacks by providing robust, reusable solutions for common callback handling scenarios.

Core Callback Utilities #

Universal Safe Callback Executor #

A comprehensive utility for safe callback execution with multiple safety checks:

Advanced Callback Manager #

A class for managing multiple callbacks with lifecycle hooks:

Async Callback Wrapper #

Handle both synchronous and asynchronous callbacks uniformly:

Callback Chain Builder #

Build and execute callback chains with error resilience:

Quick Reference Utilities #

Essential one-liner utilities for immediate use:

Production Patterns #

Copy-paste ready patterns for production use:

// Global error boundary for callbacks
window.safeCallback = (fn, ...args) => {
  try {
    return typeof fn === 'function' ? fn(...args) : undefined;
  } catch (error) {
    console.error('Callback error:', error);
    return undefined;
  }
};

// Event handler with automatic cleanup
class SafeEventHandler {
  constructor(element) {
    this.element = element;
    this.listeners = new Map();
  }
  
  on(event, callback) {
    if (typeof callback !== 'function') return this;
    
    const safeCallback = (...args) => {
      try {
        return callback(...args);
      } catch (error) {
        console.error(`Event handler error for ${event}:`, error);
      }
    };
    
    this.element.addEventListener(event, safeCallback);
    this.listeners.set(event, safeCallback);
    return this;
  }
  
  off(event) {
    const callback = this.listeners.get(event);
    if (callback) {
      this.element.removeEventListener(event, callback);
      this.listeners.delete(event);
    }
    return this;
  }
  
  destroy() {
    for (const [event, callback] of this.listeners) {
      this.element.removeEventListener(event, callback);
    }
    this.listeners.clear();
  }
}

These utilities provide comprehensive solutions for how to fix undefined is not a function error in JavaScript callbacks, covering everything from basic validation to advanced async patterns and production-ready error handling.