Reset and Clear Functionality

Relevant source files

The following files were used as context for generating this wiki page:

• calculator.html
• README.md
• LICENSE
• .github/workflows/static.yml
• index.html (Identical to calculator.html in this project context)

The Reset and Clear Functionality in the Calculator application provides users with mechanisms to revert the application state, wipe current calculations, and manage historical data. This system ensures that the internal state variables—current, previous, and operator—are properly synchronized with the Document Object Model (DOM) elements to prevent calculation errors and maintain a clean user interface.

This functionality is divided into two primary scopes: the Global State Reset (AC), which clears the immediate calculation registers, and the History Clear, which purges the persistent log of previous calculations stored during the session.

Application State Reset

The core of the reset logic resides in the handleClear function. This function is responsible for zeroing out the internal calculation engine. It targets the four primary state variables that track the user's progress through a mathematical expression.

State Variable Management

When a clear action is triggered, the following state transitions occur:

Variable	Reset Value	Description
current	'0'	The value currently being typed or displayed.
previous	''	The operand stored before an operator was selected.
operator	null	The arithmetic operation currently pending.
shouldReset	false	A boolean flag indicating if the next digit input should overwrite the display.

Sources: calculator.html:362-365

UI Synchronization

The reset process concludes by updating the UI components to reflect the clean state. The updateDisplay('0') call ensures the main output reads "0", and updateExpr('') clears the secondary expression line above the main result.

Sources: calculator.html:436-439

The following flowchart illustrates the logic flow when the "AC" button or the Escape key is pressed:

The diagram shows how the system handles both UI interactions and keyboard shortcuts to achieve a synchronized reset.
Sources: calculator.html:436-439, calculator.html:470, calculator.html:482

History Clear Functionality

The history system maintains an array of objects representing previous calculations. The clear functionality for this module is decoupled from the main calculator reset to allow users to clear their workspace without losing their calculation log, or vice versa.

History List Purging

The clear history action targets the history array and the historyList DOM container. It performs the following operations:

1. Array Truncation: Re-initializes the history array to an empty state [].
2. DOM Re-rendering: Calls renderHistory(), which removes all existing .history-item elements from the view.
3. Empty State Toggle: Displays the #historyEmpty message ("No calculations yet") once the list is empty.

Sources: calculator.html:459-462, calculator.html:446-447

Sequence of History Erasure

The interaction between the user and the history management system is depicted below:

This sequence ensures that the persistent record of session calculations is fully removed from both memory and the interface.
Sources: calculator.html:446-457, calculator.html:459-462

Input Overwrite (Implicit Reset)

The system implements a "soft reset" or "overwrite" logic using the shouldReset flag. This is not a manual clear operation but an automated state management feature that occurs after a calculation is completed or an operator is selected.

• Trigger: Setting shouldReset = true happens after handleOp or handleEquals.
• Action: When inputDigit is called while shouldReset is true, the current value is replaced by the new digit rather than appended, effectively resetting the input buffer for the next part of the calculation.

Sources: calculator.html:388-390, calculator.html:405, calculator.html:432

function inputDigit(d) {
  if (shouldReset) { 
    current = d === '0' ? '0' : d; 
    shouldReset = false; 
  }
  // ... rest of logic
}

Sources: calculator.html:388-393

Summary of Triggers

Reset and clear actions can be invoked through multiple interfaces:

Action	UI Element	Keyboard Shortcut	Function
All Clear	.btn-fn[data-action="clear"]	Escape	handleClear()
Clear History	#clearHistory	N/A	Anonymous Arrow Function
Input Reset	N/A (Automatic)	Any Digit (Post-equals)	inputDigit() logic

Sources: calculator.html:267, calculator.html:314, calculator.html:470, calculator.html:482