How to Verify Integer Variables in JavaScript and Raise Errors for Non-Integer Values

Determining if a JavaScript variable represents an integer can be crucial. Several approaches are available to perform this check effectively.

Option 1: Using isNaN and Parsing for Cast

The example provided in the question attempts to use NaN(data) to check for integers. However, this approach is not reliable. Instead, consider the following function:

function isInt(value) {
  return !isNaN(value) && parseInt(Number(value)) == value && !isNaN(parseInt(value, 10));
}

This function ensures thorough checking by parsing the potential integer into a number and comparing it to the original value.

Option 2: Using Bitwise Operations

Simple Parsing and Checking

function isInt(value) {
  var x = parseFloat(value);
  return !isNaN(value) && (x | 0) === x;
}

This approach parses the input as a float and checks if the result is equal to the original value, confirming integer representation.

Short-Circuiting for Enhanced Performance

function isInt(value) {
  if (isNaN(value)) {
    return false;
  }
  var x = parseFloat(value);
  return (x | 0) === x;
}

This short-circuits the check by first verifying if the input is not a number.

Performance Considerations

Benchmarking reveals that the short-circuiting solution offers optimal performance for this integer check.