如何在我的计算器中实现 try 和 catch 以防止错误？

Question

If my input is 6++ I'm getting 6++ as the output, rather I want an 'err' in the output. How can I implement try and catch in my code to throw the error? ex inputs: 6++ output: err, input: 5+-3 output: err, etc.

Here's my code:

 let string = ""; let buttons = document.querySelectorAll('.button'); Array.from(buttons).forEach((button) => { button.addEventListener('click', (e) => { if (e.target.innerHTML == '=') { string = eval(string); document.querySelector('input').value = string; } else if (e.target.innerHTML == 'C') { string = " "; document.querySelector('input').value = string; } else { console.log(e.target) string = string + e.target.innerHTML; document.querySelector('input').value = string; } }) })

Answer 1

Simply put try and catch around the code that calls eval() .

Note that 5+-3 is perfectly fine in JavaScript, it's equivalent to 5-3 , so you won't get an error for that.

 let string = ""; let buttons = document.querySelectorAll('.button'); Array.from(buttons).forEach((button) => { button.addEventListener('click', (e) => { if (e.target.innerHTML == '=') { try { string = eval(string); document.querySelector('input').value = string; } catch (e) { document.querySelector('input').value = "error: " + e; } } else if (e.target.innerHTML == 'C') { string = " "; document.querySelector('input').value = string; } else { console.log(e.target) string = string + e.target.innerHTML; document.querySelector('input').value = string; } }) })