When are prompt values treated as strings and when aren't they?

Question

javascript
var answer= prompt("What is 2 + 2?");
if (answer == 4) {
    alert("You are a bad ass!");}
else if (answer==3 || answer==5){
    alert("You are almost there!");}
else {
    alert("Just embarassing.");}

As we know prompts return strings, but even though I forgot to put quot. marks around 3, 4, and 5 in my code, the program works.  So then I figured because it was a "numerical string", it returned a number, but that wasnt the case either.  what is going on here?

Dino Paškvan · Accepted Answer

Something called type coercion is happening here. The == operator attempts to convert operands to the same type if they're not the same type.
JavaScript also has a strict equality operator (===), also known as the identity operator, which checks for both value and type. If you try using it instead of == you'll see that the code will work differently.
Read more about it on the MDN (https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Comparison_Operators#Using_the_Equality_Operators).

Ryan Scharfer · Answer

thanks richard and dino!

Richard Duncan · Answer

The equality operator == does type conversions for you. So when comparing 3 and "3" the equality operator will attempt to convert them to a string, number or boolean to get a match.
If you wanted to enforce a numeric or string comparison from your prompt you could use the identity operator === where this conversion is not done and the types must also be the same to be considered equal.

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Ryan Scharfer

Ryan Scharfer

When are prompt values treated as strings and when aren't they?

3 Answers

Dino Paškvan

Dino Paškvan

Richard Duncan

Richard Duncan

Ryan Scharfer

Ryan Scharfer