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JavaScript

Posted by Christopher McGurn
.a{fill-rule:evenodd;}techdegree
Christopher McGurn
Full Stack JavaScript Techdegree Student 4,771 Points

Sharing my solution

Super happy with this result! Figured I'd show my solution to share my approach to certain parts of the task.

alert('It\'s time to do some math!');

const firstNumberInput = prompt('Enter a number:');
const firstNumber = parseFloat(firstNumberInput);
const secondNumberInput = prompt('Enter another number:');
const secondNumber = parseFloat(secondNumberInput);

if (firstNumber && secondNumber) {
  const message = `
    <h1>Math with the numbers ${firstNumber} and ${secondNumber}</h1>
    ${firstNumber} + ${secondNumber} = ${firstNumber + secondNumber}<br>
    ${firstNumber} * ${secondNumber} = ${firstNumber * secondNumber}<br>
    ${firstNumber} / ${secondNumber} = ${firstNumber / secondNumber}<br>
    ${firstNumber} - ${secondNumber} = ${firstNumber - secondNumber}<br>
  `;
  document.write(message);
} else {
  alert('Please enter two valid numbers.');
}

3 Answers

Steven Parker
Steven Parker
231,141 Points
Steven Parker
Steven Parker
231,141 Points

Using a template literal is a logical and effectively equivalent output method. :+1:

But combining numbers with the Boolean "and" operator (&&) is not an effective way to test for number validity. That's what the "isNaN" function is for.

To see the problem, try using 0 as one of the "valid numbers". :see_no_evil:

Christopher McGurn
seal-mask
.a{fill-rule:evenodd;}techdegree
Christopher McGurn
Full Stack JavaScript Techdegree Student 4,771 Points
Christopher McGurn
.a{fill-rule:evenodd;}techdegree
Christopher McGurn
Full Stack JavaScript Techdegree Student 4,771 Points

Oh! I think I see what the problem is there. A string input value of '0' is considered a falsy value thus returns false in the condition. Is this correct?

Steven Parker
Steven Parker
231,141 Points
Steven Parker
Steven Parker
231,141 Points

Any non-empty string would be considered "truthy", including "0".

But they aren't strings at that point, they have been converted to numbers with "parseFloat". Then the "and" operator converts the terms into Boolan, and a 0 value translates to false.

Christopher McGurn
seal-mask
.a{fill-rule:evenodd;}techdegree
Christopher McGurn
Full Stack JavaScript Techdegree Student 4,771 Points
Christopher McGurn
.a{fill-rule:evenodd;}techdegree
Christopher McGurn
Full Stack JavaScript Techdegree Student 4,771 Points

Thank you for the information!