35 lines
1.2 KiB
Markdown
35 lines
1.2 KiB
Markdown
---
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title: Truthy Value
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---
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A **truthy** value is a value that translates to **true** when evaluated in a _Boolean_ context.
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All values are **truthy** unless they are defined as **falsy** (i.e. except for `false`, `0`, `""`, `null`, `undefined` and `NaN`).
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Some interesting **truthy** values are:
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'0' (a string containing a single zero)
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'false' (a string containing the text “false”)
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[] (an empty array)
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{} (an empty object)
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function(){} (an “empty” function)
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**Rules:**
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* `false`, `zero` and `''`(empty strings) are all equivalent.
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* `null` and `undefined` are equivalent to themselves and each other but nothing else.
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* `NaN` is not equivalent to anything – including another `NaN!
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* `Infinity` is truthy – but cannot be compared to `true` or `false`!
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* An empty array(`[]`) is truthy – yet comparing with `true` is `false` and comparing with `false` is `true`?!
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A single value can therefore be used within conditions, e.g.
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if (value) {
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// value is truthy
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}
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else {
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// value is falsy
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// it could be false, 0, '', null, undefined or NaN
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}
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See also: <a>falsy</a> | <a href='https://developer.mozilla.org/en-US/docs/Glossary/Truthy' target='_blank' rel='nofollow'>MDN</a>
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