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ob.js

ob.js comes from Vue.js. It's a small, efficient library for observing changes to javascript Object, Array and Class.

Installation

npm install --save ob.js

or

bower install --save ob.js

Usage

To watch expression. ob.watch(target, expression, callback) or ob(target, expression, callback)

Try it on: codepen jsfiddle

const target = {a: 1}
ob(target, 'a', function (newValue, oldValue) {
  console.log(newValue, oldValue)
})
target.a = 3
// 3 1

To add computed property. ob.compute(target, name, getter)

Try it on: codepen jsfiddle

const target = {a: 1}
ob.compute(target, 'b', function () {
  return this.a * 2
})
console.log(target.b)
// 2
target.a = 3
console.log(target.b)
// 6

To watch expressions and computed properties. ob.react(options)

Try it on: codepen jsfiddle

const options = {
  data: {
    PI: Math.PI,
    radius: 1,
  },
  computed: {
    'area': function () {
      return this.PI * this.square(this.radius) // πr²
    },
  },
  watchers: {
    'area': function (newValue, oldValue) {
      console.log(`area: ${newValue}`)
    },
  },
  methods: {
    square (num) {
      return num * num
    },
  },
}
const target = ob.react(options)
target.radius = 3
// area: 28.274333882308138

API

properties

name	type	value	detail
ob.deep	Boolean	The default is false	If true, ob.watch(target, expression, callback) will observe target deeply
ob.sync	Boolean	The default is false	If true, ob.watch(target, expression, callback) will invoke callback immediately when a property change is detected
ob.default	Function	Could only be one of ob.react, ob.watch and ob.compute. The default is ob.watch	Set actual method to ob.default for ob(...)

methods

ob(...)

• It's syntactic sugar of ob.default. See 'properties' for details

ob.watch(target, expression, callback)

• target: Any object
• expression: String or Function
• callback: Function
• Returns Watcher. And calling watcher.teardown() could unwatch expression

ob.compute(target, name, accessor, cache)

• target: Any object
• name: String
• accessor:
  • Function: It will be the get of accessor
  • Object: Contains: (at least get or set)
    • get: Function
    • set: Function
    • cache: Boolean. Optional. The default is true. If false, the get will be evaluated whenever reading computed properties
• cache: Boolean. Same as accessor.cache

ob.react(options, target)

• options: Object. Contains:
  • data: It's the properties to add
  • computed: It's the computed properties to add
  • watchers: It's the watchers to watch properties or computed properties
  • methods: The methods to add. And these will bind to target
• target: Any object. Optional. The default is empty object. It will be attached with the fields of options
• returns target

License

MIT