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86 lines
2.7 KiB
86 lines
2.7 KiB
4 years ago
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expr
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=======
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Tiny expression helper for creating compiled accessors; handles most stuff, including ["bracket notation"] for property access. Originally based off of Kendo UI Core expression code
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npm install property-expr
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## Use
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Setters and getters are compiled to functions and cached for Performance™
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var expr = require('property-expr')
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, obj = {
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foo: {
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bar: [ "hi", { buz: { baz: 'found me!' } }]
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}
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};
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var getBaz = expr.getter('foo.bar[1]["buz"].baz')
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, setBaz = expr.setter('foo.bar[1]["buz"].baz')
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console.log(getBaz(obj)) // => 'found me!'
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setBaz(obj, 'set me!')
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console.log(obj.foo.bar[1].buz.baz) // => 'set me!'
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### `getter(expression, [ safeAccess ])`
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Returns a function that accepts an obj and returns the value at the supplied expression. You can create a "safe" getter, which won't error out when accessing properties that don't exist, reducing existance checks befroe property access:
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expr.getter('foo.bar.baz', true)({ foo: {} }) // => undefined
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//instead of val = foo.bar && foo.bar.baz
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### `setter(expression)`
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Returns a function that accepts an obj and a value and sets the property pointed to by the expression to the supplied value.
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### `expr(expression, [ safeAccess], [ paramName = 'data'])`
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Returns a normalized expression string pointing to a property on root object
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`paramName`.
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expr.expr("foo['bar'][0].baz", true, 'obj') // => "(((obj.foo || {})['bar'] || {})[0])"
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### `split(path) -> Array`
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Returns an array of each path segment.
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```js
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expr.split("foo['bar'][0].baz") // [ "foo", "'bar'", "0", "baz"]
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```
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### `forEach(path, iterator[, thisArg])`
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Iterate through a path but segment, with some additional helpful metadata about the segment. The iterator function is called with: `pathSegment`, `isBracket`, `isArray`, `idx`, `segments`
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```js
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expr.forEach('foo["bar"][1]', function(pathSegment, isBracket, isArray, idx, segments) {
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// 'foo' -> isBracket = false, isArray = false, idx = 0
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// '"bar"' -> isBracket = true, isArray = false, idx = 1
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// '0' -> isBracket = false, isArray = true, idx = 2
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})
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```
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### `normalizePath(path)`
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Returns an array of path segments without quotes and spaces.
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```js
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expr.normalizePath('foo["bar"][ "1" ][2][ " sss " ]')
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// ['foo', 'bar', '1', '2', ' sss ']
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```
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### `new Cache(maxSize)`
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Just an utility class, returns an instance of cache. When the max size is exceeded, cache clears its storage.
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```js
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var cache = new Cache(2)
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cache.set('a', 123) // returns 123
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cache.get('a') // returns 123
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cache.clear()
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cache.set('a', 1)
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cache.set('b', 2) // cache contains 2 values
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cache.set('c', 3) // cache was cleaned automatically and contains 1 value
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```
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