Quick Reference
The JavaScript isFinite() method returns “true” if a value is a finite number (not Infinity, -Infinity, or NaN).
The value is first converted to a number and then tested as to whether it is a finite number.
<!-- html element to place output -->
<p id="my_output"></p>// variable
let my_number = isFinite(123);
// output to the HTML element
document.getElementById('my_output').innerHTML = my_number;Note
Don’t confuse this with the Number.isFinite() method which does NOT convert the value first. So in that case, if the value is not a number, it will return FALSE. The global isFinite() method first converts the value to a number and then tests it as to whether it is a finite number. So even if the value starts as a string, if when converted it becomes a number, it can be tested to be TRUE or FALSE.
Output
trueSyntax
isFinite(value)JavaScript Notes:
- When using JavaScript, single or double quotation marks are acceptable and work identically to one another; choose whichever you prefer, and stay consistent
- JavaScript is a case-sensitive language; firstName is NOT the same as firstname
- Arrays count starting from zero NOT one; so item 1 is position [0], item 2 is position [1], and item 3 is position [2] … and so on
- JavaScript variables must begin with a letter, $, or _
- JavaScript variables are case sensitive (x is not the same as X)
We’d like to acknowledge that we learned a great deal of our coding from W3Schools and TutorialsPoint, borrowing heavily from their teaching process and excellent code examples. We highly recommend both sites to deepen your experience, and further your coding journey. We’re just hitting the basics here at 1SMARTchicken.