Validate number if statement JavaScript

Question

I have the following statement where I just want to validate that user does not leave fields empty. My problem is at productPrice, if I uncomment those three lines, it will not work and get into else block even if the number I provide meets the criteria. If I leave it so only with productPrice != "" it will allow any string as value for price into the database. What is wrong here?

if (
    productTitle != "" &&
    productPrice != "" &&
    // Number.isInteger(productPrice) &&
    // productPrice > 0 &&
    // productPrice < 1000 &&
    productDescription != ""
) {
    let productData = {
        title: productTitle,
        price: productPrice,
        description: productDescription,
    };

    // .....
} else {
    console.log("All fields required");
}

how can a variable be a string and a number at the same time? — Ramesh Reddy
– Ramesh Reddy, Commented Jul 11, 2020 at 10:50
You can just remove productPrice != "" && and use the rest of the commented conditions. — Ramesh Reddy
– Ramesh Reddy, Commented Jul 11, 2020 at 10:51
You can avoid unnecessary checks like string comparison and parsing if you use an <input type="number" /> — SamwellTarly
– SamwellTarly, Commented Jul 11, 2020 at 11:20

LoukasPap · Accepted Answer · 2020-07-11 11:29:12Z

1

You can convert productPrice from String, to Number(Integer), and then try compare with 0 & 1000.

var pp = parseInt(productPrice) || 0;

if(
 ...
 !isNan(productPrice) &&
 pp > 0 &&
 pp < 1000 &&
 ...
){...

In the 1st line, we check if productPrice is NaN, so as to catch this exception.

edited Jul 11, 2020 at 11:29

answered Jul 11, 2020 at 11:08

LoukasPap

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2 Comments

SamwellTarly Over a year ago

I suggest you improve your answer by telling the user how to check for NaN. Don't want them to do a string comparison :)

LoukasPap Over a year ago

For exmaple, isNaN(productPrice)?

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