shawncplus / memoization-behavior

Polymer behavior adding memoization helpers

memoization-behavior

====================

Biddle.MemoizationBehavior allows you to define a computed property as memoizable (http://en.wikipedia.org/wiki/Memoization) with _memoizeComputed or more generally memoize any given function with _memoize

Note: Methods of this behavior are "private" as a matter of convention and will not appear on beta.webcomponents.org hosted documentation. I've made the executive decision that it wouldn't be wise to allow the memoization methods to be published as part of an element's public API. Doing so may entice some hapless individual into creating some kind of element whose purpose is to memoize all computed properties in all elements ever.

To implement a computed property as memoizable in the simplest fashion (although this is a trivial example, you would likely only want to memoize expensive functions)

behaviors: [
    Biddle.MemoizationBehavior,
],

properties: {
    firstName: String,
    lastName: String,
    fullName: {
        type: String,
        computed: '_memoizeComputed("fullName", firstName, lastName)'
        method: '_getFullName'
    }
},

_getFullName: function (first, last) {
    return first + ' ' + last;
}

Given that the default hash function is JSON.stringify which may be inappropriate for object/array parameters you may wish to override the default hashing method for a specific property.

properties: {
    foo: Object,
    bar: Object,
    foobar: {
        type: String,
        computed: '_memoizeComputed("fullName", foo, bar)'
        method: '_computeFoobar',
        hashFn: (foo, bar) => foo.id + ':' + bar.id
    }
},

To generally memoize any function you may do the following

var someValue = this._memoize(this.someExpensiveFunction)(arg2, arg2, arg3);

Cache invalidation happens manually with the _invalidateMemoizeCache method

var foo = this._memoize(this.bar)('Hello');
// ...
this._invalidateMemoizeCache(this.bar);