54ed736e28
Adds a simple `checkProp` factory function for re-usable utility predicates. The reason the predicate comes before the prop is to signify the predicate will be called with the prop, however I have no desire to make that a hard requirement. Order can easily be changed.
30 lines
869 B
Markdown
30 lines
869 B
Markdown
### checkProp
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Given a `predicate` function and a `prop` string this curried function will then take an `object` to inspect by calling the property and passing it to the predicate.
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It summons `prop` on `obj` and passes it to a provided `predicate` function and returns a masked boolean
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```js
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const checkProp = (predicate, prop) => obj => !!predicate(obj[prop])
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```
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```js
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const lengthIs4 = checkProp(l => l === 4, 'length')
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lengthIs4([]) // false
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lengthIs4([1,2,3,4]) // true
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lengthIs4(new Set([1,2,3,4]) // false (Set uses Size, not length)
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const session = { user: {} }
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const validUserSession = checkProps(u => u.active && !u.disabled, 'user')
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validUserSession(session) // false
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session.user.active = true
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validUserSession(session) // true
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const noLength(l => l === undefined, 'length')
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noLength([]) // false
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noLength({}) // true
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noLength(new Set()) // true
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```
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