Echo

Echo provides screen output functionality — printing formatted text to HTML elements or custom output handlers. It maintains an internal stream that captures all printed content, useful for debug pages and test output.

Package: io-oidis-commons

import { Echo } from "@io-oidis-commons/.../Utils/Echo.js";

Initialization

Echo.Init($targetIdOrHandler? : string | IOHandler, $forceInit? : boolean) : void

Initialize Echo with an output target. If called without arguments, it defaults to an HTML element with id="Content":

// Default — targets element with id="Content"
Echo.Init();

// Target a specific HTML element by ID
Echo.Init("outputPanel");

// Use a custom IOHandler
Echo.Init(myCustomHandler);

// Force re-initialization (overwrite existing handler)
Echo.Init("newTarget", true);

note

In most Oidis test pages and debug views, an element with id="Content" exists by convention, so calling Echo.Init() without arguments works out of the box.

Printing Methods

Echo.Print($message : string, $clearBeforePrint? : boolean) : void
Echo.Println($message : string) : void
Echo.Printf($messageOrObject : string | any, ...$parameters : any[]) : void
Echo.PrintCode($message : string) : void

// Print raw text
Echo.Print("Hello");

// Print and clear previous content first
Echo.Print("Fresh start", true);

// Print with newline
Echo.Println("Line 1");
Echo.Println("Line 2");

// Printf — formatted output with positional placeholders
Echo.Printf("User {0} has {1} items", userName, count);

// Printf — object inspection (auto-converts non-string to readable output)
Echo.Printf(complexObject);

// Print code block (HTML-escaped, in <pre> tags)
Echo.PrintCode("<div>This shows as escaped HTML</div>");

Printf Formatting

Printf is the most versatile print method. It accepts either:

• A string with {0}, {1}, ... placeholders (uses StringUtils.Format internally)
• Any object — automatically converted to a readable string representation

// String formatting
Echo.Printf("Status: {0}, Items: {1}, Total: {2}", status, items.length, total);

// Object inspection (useful for debugging)
Echo.Printf(response.data);
Echo.Printf({ action: "save", records: modified.length });

Screen Management

Echo.Clear() : void       // Clear screen content (keep stream)
Echo.ClearAll() : void    // Clear screen content AND stream

Echo.Println("Step 1 complete");
Echo.Println("Step 2 complete");

Echo.Clear();     // Screen is empty, but stream still has both lines
Echo.ClearAll();  // Screen is empty AND stream is reset

Stream Capture

Echo.getStream() : string

Returns the complete content stream since the last ClearAll(). Useful for capturing test output or building reports:

Echo.ClearAll();
Echo.Println("Test 1: PASS");
Echo.Println("Test 2: PASS");
Echo.Println("Test 3: FAIL");

const results = Echo.getStream();
// → "Test 1: PASS\nTest 2: PASS\nTest 3: FAIL\n"

Event Callback

Echo.setOnPrint($handler : ($message : string) => void) : void

Set a callback that fires every time a message is printed. Useful for forwarding output to additional targets:

Echo.setOnPrint(($message) => {
    LogIt.Info("Echo output:", $message);
    // Or forward to a WebSocket, file, etc.
});

Handler Type

Echo.getHandlerType() : IOHandlerType

Returns the type of the currently active output handler (HTML element, custom handler, etc.).

When to Use Echo

Scenario	Use Echo	Use LogIt
Debug/test page output	Yes	No — LogIt goes to console
Visible on-screen results	Yes	No
Development debugging	No	Yes
Production error logging	No	Yes
Capturing output as string	Yes (getStream)	No

tip

Echo is for visible screen output — debug pages, test result displays, and interactive demos. For development debugging that goes to the console/terminal, use LogIt. For persistent audit trails, use SystemLog.

Complete Method Reference

Method	Description
Init($target?, $force?)	Initialize with element ID or IOHandler
getHandlerType()	Current output handler type
Print($message, $clear?)	Print raw text
Println($message)	Print with newline
Printf($msgOrObj, ...$params)	Formatted print or object inspection
PrintCode($message)	Print in <pre> with escaped HTML
Clear()	Clear screen (keep stream)
ClearAll()	Clear screen and stream
getStream()	Get captured content stream
setOnPrint($handler)	Set print event callback

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See also: Utilities Overview | Logging | StringUtils | Convert