jQuery jQuery.isNumeric() Method

What You’ll Learn

The jQuery.isNumeric() utility returns true when a value is a finite number or a string that parses as one. This tutorial covers syntax, five worked examples from the official API, comparisons with isNaN(), form validation patterns, and values that fail the test.

Introduction

Form fields, plugin options, and AJAX payloads often arrive as strings — even when they represent numbers. Before you call parseInt, do math, or pass a value to a jQuery animation duration, you need to know whether the input is actually numeric.

jQuery provides jQuery.isNumeric() (also written $.isNumeric()) as a single boolean test. It accepts numbers and numeric strings, rejects empty strings, booleans, NaN, Infinity, and values like "10px" that only partially parse as numbers.

Understanding the jQuery.isNumeric() Method

jQuery.isNumeric(value) returns true only when value is a number or string whose entire content represents a finite numeric value. Internally jQuery checks the type, parses when needed, and verifies the result is not NaN or infinite.

Use it in validation helpers, slider widgets, quantity inputs, and anywhere user text must be confirmed as a plain number before calculation — not as a replacement for range checks or business rules.

📝 Syntax

General form of jQuery.isNumeric:

jQuery.isNumeric( value )
// or
$.isNumeric( value )

Parameters

• value — any JavaScript value to test.

Return value

• true if value is a finite number or numeric string.
• false for all other types and non-numeric strings.

Minimal workflow

var raw = $("#quantity").val();
if ($.isNumeric(raw)) {
  var qty = parseFloat(raw);
}

Examples Gallery

Each example uses $.isNumeric(). Open DevTools or use the Try-it links to run them interactively.

console.log($.isNumeric(10));    // true
console.log($.isNumeric("10"));  // true
console.log($.isNumeric("-10")); // true
console.log($.isNumeric(0));     // true

true
true
true
true

console.log($.isNumeric(""));        // false
console.log($.isNumeric(true));      // false
console.log($.isNumeric(NaN));       // false
console.log($.isNumeric(Infinity));  // false
console.log($.isNumeric("10px"));    // false

false (×5)

console.log($.isNumeric(-3.14));    // true
console.log($.isNumeric("-3.14"));  // true
console.log($.isNumeric("0.5"));     // true

true
true
true

function validateQuantity(val) {
  if (!$.isNumeric(val)) {
    return "Enter a valid number";
  }
  var n = parseFloat(val);
  if (n < 1) {
    return "Minimum quantity is 1";
  }
  return "OK: " + n;
}

console.log(validateQuantity("5"));   // OK: 5
console.log(validateQuantity("abc")); // Enter a valid number

OK: 5
Enter a valid number

console.log(isNaN(""));           // false — "" coerces to 0!
console.log($.isNumeric(""));     // false — correct for empty input

console.log(typeof NaN);           // "number"
console.log($.isNumeric(NaN));     // false

false
false
number
false

🚀 Common Use Cases

• Form validation — quantity, age, price, and rating fields.
• Plugin options — confirm duration, opacity, or index values are numeric.
• Animation helpers — validate speed/delay before passing to .animate().
• CSV / paste parsing — filter rows where a column should be numeric.
• AJAX payloads — guard string fields that must parse as numbers.
• Legacy jQuery UI — consistent numeric checks across older widgets.

📝 Notes

• Available since jQuery 1.7.
• Accepts negative numbers and decimal strings.
• Rejects hex strings like "0xFF" and strings with units like "10px".
• Does not validate integer-only — use extra checks after isNumeric.
• Whitespace-only strings typically fail — trim input first if needed.
• Related: $.type() returns "number" for NaN — pair with isNumeric for input validation.

💡 Best Practices