Published
Edited
Oct 5, 2020
Insert cell
Insert cell
typeof undefined
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{
let value;
return typeof value;
}
Insert cell
{
let value;
return value === undefined;
}
Insert cell
{
// uh-oh!
const undefined = 'not undefined';
let value;
return value === undefined;
}
Insert cell
{
const undefined = 'not undefined';
let value;
return typeof value === 'undefined';
}
Insert cell

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Observable is your go-to platform for exploring data and creating expressive data visualizations. Use reactive JavaScript notebooks for prototyping and a collaborative canvas for visual data exploration and dashboard creation.
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