How do you chain operations in a calculator in JavaScript?
When a new operation is set and there is already a pending operation, calculate the pending operation first (calculate()), then store the result as the new previous and set the new operation. This allows chaining like 5 + 3 * 2.
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More FAQs in How to Build a Calculator in an Interview
Track current input, previous value, and operation. Number buttons append to current. Operation buttons store the operation and previous value. Equals performs the calculation. Clear resets everything. Use a grid layout for buttons.
Check if the divisor is 0 before dividing. If so, display 'Error' or 'Cannot divide by zero' instead of performing the calculation. Do not let JavaScript produce Infinity; handle it explicitly.
Add a keydown listener. Map number keys to inputChar, operator keys to setOp, Enter/= to calculate, Escape to clear, and decimal to inputChar('.'). Prevent default for Enter to avoid form submission.
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