Member Avatar for covertx
covertx 0 Newbie Poster

.

  • 1 Contributor
  • 0 Replies
  • 79 Views

Dani AI

Generated

posted a minimal message; below is a concise, practical reference for JavaScript's Math.round with common pitfalls and a small utility for rounding to a fixed number of decimals.

Math.round(x) returns the numeric value x rounded to the nearest integer. Ties (fractional part exactly .5) are resolved toward +Infinity (for example, Math.round(1.5) is 2 and Math.round(-1.5) is -1). Arguments are coerced to Number; invalid conversions yield NaN. Official documentation and the ECMAScript definition are available here: MDN - Math.round and ECMAScript spec (Math.round).

Example behaviors:

Math.round(1.4);   // 1
Math.round(1.5);   // 2
Math.round(-1.5);  // -1
Math.round(NaN);   // NaN

To round to a fixed number of decimal places, a common pattern is shown below; Number.EPSILON helps reduce binary floating-point surprises but is not a perfect solution for all cases:

function roundTo(num, decimals) {
  var factor = Math.pow(10, decimals);
  return Math.round((num + Number.EPSILON) * factor) / factor;
}

roundTo(1.005, 2); // 1.01 (expected)

For financial or exact decimal requirements, integer arithmetic (cents) or a decimal library is recommended instead of relying on floating-point tricks (see decimal.js on GitHub).

Be a part of the DaniWeb community

We're a friendly, industry-focused community of developers, IT pros, digital marketers, and technology enthusiasts meeting, networking, learning, and sharing knowledge.