js check if number is whole number (integer)

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console.log(Number.isInteger(+123));       // true
console.log(Number.isInteger(-123));       // true

console.log(Number.isInteger(3.14));       // false
console.log(Number.isInteger(NaN));        // false
console.log(Number.isInteger(null));       // false
console.log(Number.isInteger(undefined));  // false
console.log(Number.isInteger(true));       // false
console.log(Number.isInteger(false));      // false
console.log(Number.isInteger(''));         // false
console.log(Number.isInteger('123'));      // false


// Note: Number.isInteger() method is supported in the major web browsers since 2014-2015.

// See also:
//
//     1. https://dirask.com/snippets/js-check-if-number-is-whole-number-integer-jQzEQ1

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const isInteger = (value) => {
    if (Number.isFinite(value)) {
        return value % 1 === 0;
    }
    return false;
};


// Usage example:

console.log(isInteger(+123));       // true
console.log(isInteger(-123));       // true

console.log(isInteger(3.14));       // false
console.log(isInteger(NaN));        // false
console.log(isInteger(null));       // false
console.log(isInteger(undefined));  // false
console.log(isInteger(true));       // false
console.log(isInteger(false));      // false
console.log(isInteger(''));         // false
console.log(isInteger('123'));      // false