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46 lines
1.4 KiB
JavaScript
46 lines
1.4 KiB
JavaScript
"use strict";
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var method = require("../method/core")
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// Method is designed to work with data structures representing application
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// state. Calling it with a state should return object representing `delta`
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// that has being applied to a previous state to get to a current state.
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//
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// Example
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//
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// diff(state) // => { "item-id-1": { title: "some title" } "item-id-2": null }
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var diff = method("diff@diffpatcher")
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// diff between `null` / `undefined` to any hash is a hash itself.
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diff.define(null, function(from, to) { return to })
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diff.define(undefined, function(from, to) { return to })
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diff.define(Object, function(from, to) {
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return calculate(from, to || {}) || {}
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})
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function calculate(from, to) {
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var diff = {}
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var changes = 0
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Object.keys(from).forEach(function(key) {
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changes = changes + 1
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if (!(key in to) && from[key] != null) diff[key] = null
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else changes = changes - 1
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})
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Object.keys(to).forEach(function(key) {
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changes = changes + 1
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var previous = from[key]
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var current = to[key]
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if (previous === current) return (changes = changes - 1)
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if (typeof(current) !== "object") return diff[key] = current
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if (typeof(previous) !== "object") return diff[key] = current
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var delta = calculate(previous, current)
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if (delta) diff[key] = delta
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else changes = changes - 1
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})
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return changes ? diff : null
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}
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diff.calculate = calculate
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module.exports = diff
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