JavaScript: Number.isFinite

Number.isFinite ( number )

1. If type of number is not number, return false.
2. If number is NaN, +Infinity, or -Infinity, return false.
3. Else, return true.

〔►see JavaScript: Data Types〕

console.log ( Number.isFinite ( 3 ) ); // true
console.log ( Number.isFinite ( 3.4 ) ); // true

console.log ( Number.isFinite ( "3" ) ); // false
console.log ( Number.isFinite ( Infinity ) ); // false
console.log ( Number.isFinite ( NaN ) ); // true

Reference

ECMAScript® 2016 Language Specification#sec-number.isfinite