is a primitive data type. It represents the intentional absence of value. In code, it is represented as `null`. codecademy 
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/null
function getVowels(str) { const m = str.match(/[aeiou]/gi); if (m === null) { return 0; } return m.length; } console.log(getVowels('sky')); // expected output: 0
In the frame below (or with the help of the DevTools) we can view the results.
//wiki.ralfbarkow.ch/assets/pages/snippet-template/esm.html HEIGHT 50
Show source code in debugger
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DOT strict digraph rankdir=LR node [style=filled fillcolor=lightyellow penwidth=3 color=black fontname="Helvetica"] HERE NODE node [style=filled fillcolor=lightblue] WHERE /^⇒/ LINKS HERE -> NODE node [style=filled fillcolor=white] HERE NODE WHERE /^⇒/ LINKS HERE -> NODE node [style=filled fillcolor=white penwidth=3 color=black] LINKS HERE -> NODE node [style=filled fillcolor=white penwidth=1 color=black] HERE NODE LINKS HERE -> NODE node [style="filled,rounded,dotted" fillcolor=white] edge [style=dotted] HERE NODE BACKLINKS NODE -> HERE