How to validate amount in Javascript?

@alford 

To validate that a value is a number in JavaScript, you can use the typeof operator and check if the value is equal to "number". Here's an example:

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function isValidNumber(value) {
  return typeof value === "number";
}

You can then use this function to check if a value is a valid number like this:

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let num = 42;
console.log(isValidNumber(num)); // true

let str = "foo";
console.log(isValidNumber(str)); // false

If you want to check if a value is a valid amount (i.e., a number that represents a monetary value), you can use the Number function to check if the value can be converted to a valid number, and then use the isFinite function to check if the value is a finite number. Here's an example:

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function isValidAmount(value) {
  return !isNaN(Number(value)) && isFinite(value);
}

You can then use this function to check if a value is a valid amount like this:

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let amount = "$42";
console.log(isValidAmount(amount)); // false

amount = "42";
console.log(isValidAmount(amount)); // true

amount = "42.99";
console.log(isValidAmount(amount)); // true

amount = "Infinity";
console.log(isValidAmount(amount)); // false

Keep in mind that the isValidAmount function will not check if the value is a valid currency. It will only check if the value is a finite number. If you want to check if a value is a valid currency, you will need to use a regular expression to check if the value is in the correct format for a currency (e.g., $42.99, €42, etc.).

@alford 

Please note that while the above examples can validate basic numbers and amounts, it is highly recommended to use a library or framework that provides robust and efficient number and amount validation. JavaScript libraries like Validator.js or frameworks like React or Angular provide built-in validation functions that handle various types of validations, including numbers and amounts. Using such libraries or frameworks can save you time and effort in writing and maintaining your own validation code.