Validate decimal numbers in JavaScript - IsNumeric()

Choose Number.isFinite over isNaN

In JavaScript's vast ocean, the Number.isFinite buoy is more reliable than isNaN or Number.isNaN. Why? Because Number.isFinite says no to Infinity and -Infinity, which are technically numbers in JavaScript, but misleading in our decimal check.

Your Robust Defense Against Errors

Remember our goal: bulletproof decimal validation. Do you know what different inputs can lurk in the dark? Boolean values, whitespace strings, hexadecimal numbers. You need to prepare for everything:

function IsNumeric(input) {
  if (typeof input === 'boolean') {  // no booleans on my watch
    return false;
  }
  const numStr = String(input).trim();  // shaving off those pesky whitespace
  const regex = /^-?\d*(\.\d+)?$/;  // regex, our knight in hexadecimal armour
  return regex.test(numStr) && !regex.test('-') && numStr !== '' && Number.isFinite(+numStr);
}
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Handling Non-Decimal Numbers

JavaScript loves hexadecimal and other numeric types, but your decimal check doesn't. Deploy additional qualifiers to handle these imposters:

function isStrictlyDecimal(value) {
  // Is it a decimal or an intruder? Let's find out.
  return /^[-+]?(\d+|\d*\.\d+)$/.test(value);
}
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Test Your Validation Skill

How about a test-driven approach with 30 different cases? Not only you get peace of mind knowing your function works, but also valuable resources for others. It's a win-win situation in the making.

Handling Arrays and Objects

Arrays and objects pretending to be numbers? Not on our watch! Differentiate them with the Object.prototype.toString.call() method:

function isNotArrayOrObject(input) {
  // If it walks like a duck, swims like a duck, quacks like a duck... It might be an array or object.
  return !['[object Array]', '[object Object]'].includes(Object.prototype.toString.call(input));
}
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The Efficiency Playbook

• Encapsulation: Protect your regex with closure, save memory, and gain efficiency.
• Type Checking: Before validation, ensure your input is meant to be numeric.

Know Your Pitfalls

Watch out for:

• Locale Specificity: Symbols like comma and period can interchange based on the locale.
• Scientific Notation: Ensure handling of inputs in scientific notation.
• Type Coercion: JavaScript can be too flexible with types. Verify before validation!