36 lines
1.6 KiB
Markdown
36 lines
1.6 KiB
Markdown
---
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title: "Tip: Convert a string to a boolean"
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shortTitle: String to boolean
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type: tip
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language: javascript
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tags: [string,boolean,type]
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author: chalarangelo
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cover: two-cities
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excerpt: Have you ever tried to convert the string representation of a boolean to an actual boolean value? Here's a simple way to do it.
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dateModified: 2022-09-14T05:00:00-04:00
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---
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Sometimes, one might run into the problem of converting the string representation of a value into the value itself. This is often straightforward, such as with numeric values. However, string representations of boolean values can be a bit trickier.
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This issue arises due to the fact that any non-empty string is considered truthy in JavaScript. On top of that, strings can have different capitalization or whitespace, making it harder to compare them directly to a constant.
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To counteract this, it's often a good idea to use a couple of transformations, namely `String.prototype.toLowerCase()` and `String.prototype.trim()`, to make the string representation of the value more consistent. Additionally, an array of acceptable values might make it easier to perform the conversion in certain cases.
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```js
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const toBoolean = (value, truthyValues = ['true']) => {
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const normalizedValue = String(value).toLowerCase().trim();
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return truthyValues.includes(normalizedValue);
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};
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toBoolean('true'); // true
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toBoolean('TRUE'); // true
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toBoolean('True'); // true
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toBoolean('tRue '); // true
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toBoolean('false'); // false
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toBoolean('FALSE'); // false
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toBoolean('False'); // false
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toBoolean('fAlse '); // false
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toBoolean('YES', ['yes']); // true
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toBoolean('no', ['yes']); // false
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```
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