JavaScript Reference
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Quick Reference

The NaN property returns NaN (Not a Number).

<!-- html element to place output -->
<p id="my_output"></p>
// variable
let my_number = NaN;

// output to the HTML element
document.getElementById('my_output').innerHTML = my_number;

Note

The global NaN property is nearly the same as the Number.NaN property, both returning NaN.

Output

NaN

Syntax

NaN

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)
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