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typescript-calculator

A class based calculator implementation with functions for evaluating mathematical expressions.

Properties

  • currentTotal: holds the current running total of the calculator
  • currentOperator: holds the active operator for the calculator
  • lastOperator: holds the last operator that was pressed
  • displayShouldClear: boolean indicating if the display should be cleared or not
  • onDisplayUpdateHandlers: an array of functions to handle display updates
  • onDisplay: holds the value currently displayed on the calculator
  • history: an array holding the history of operations performed on the calculator

Methods

  • fireDisplayUpdateHandlers: invokes all functions in onDisplayUpdateHandlers array
  • onDisplayUpdate: adds a function to the onDisplayUpdateHandlers array
  • offDisplayUpdate: removes a function from the onDisplayUpdateHandlers array
  • numberPressed: updates the display value of the calculator with the number pressed
  • removeHangingDecimal: removes hanging decimal points from the display
  • evaluate: evaluates the current mathematical expression
  • clear: resets the calculator to its initial state

Usage Examples

const calculator = new Calculator();
calculator.onDisplayUpdate((val) => console.log("Calculator display: ", val));
calculator.buttonPressed({ type: "number", value: "2" });
calculator.buttonPressed({ type: "operator", value: "+" });
calculator.buttonPressed({ type: "number", value: "2" });
calculator.evaluate();

// Output:
// Calculator display: 2
// Calculator display: 2
// Calculator display: 4