JS Object-Oriented Programming: caching of data

JS can also cache data to speed up processing. It is worthwhile to use space for time when necessary. For example, it takes a long time to complete the calculation, you can cache the results to the client, you can directly use the cached results, not to repeat the calculation.

1 caching of the computed results of a simple function 2 recursive function of the cached 3Ajax read data

1 caching of computed results for simple functions

For example:

     The common function, encapsulating internal calls, caches the result     function memorize (f) {  var cache={};  return function () {   var key=arguments.length+array.prototype.join.call (arguments, ",");//parameter length and parameter as attribute value   if ( Key in cache)//presence directly reads cache data   {     return cache[key];   }   else   {     return cache[key]=f.apply (this,arguments);//does not exist, then calculates and caches the result of the calculation}}  }

Specific use

Simulates a function    testfunction (x) {return x*x, which takes a long time to calculate  ;}  Test, call  function test () {          var t=memorize (testfunction);     var k=t (6);//The first call needs to calculate     var k2=t (6);//The second time to read the buffer directly, not to calculate  alert (K2);     }

2 caching of computed results for recursive functions

Specific use

function Test2 () {          var t=memorize (function (x) {///recursive function computes the factorial if of x     (x<=0) {return 1;}         else{return X*t (x-1)}   );     var k=t (6);//cache 6 to 1 factorial        var k2=t (7);//Only one call is required, and the cache alert (K2) is used to calculate 6 factorial  ;     }

3Ajax Cache of Read Data

The Ajax cache can also be used in a similar way, but it's still learned from Https://github.com/devbridge/jQuery-Autocomplete.

The principle is actually the same as the top.

The core sections are organized as follows:

      function Autocomplete () {this.cachedresponse = {};//cached data saved container this.badqueries = [after];//query, there are no queries that meet the criteria} autocom     Plete.prototype.clearCache = function ()//empty Cache {this.cachedresponse = {};            This.badqueries = [];                }, Autocomplete.prototype.getsuggestions=function (q) {//Read data var response, that = this, Options = that.options, serviceurl = Options.serviceurl, data, cache            Key;            Options.params[options.paramname] = q; data = Options.ignoreparams?            Null:options.params; CacheKey = serviceurl + '? ' + $.param (Data | | {});//The cached key is a URL and the passed parameter consists of response = that.cachedresponse[cachekey];//Gets the cached data if (response && $.                IsArray (response.suggestions)) {//If there is a cache that.suggestions = response.suggestions;            That.suggest ();                     } else if (!that.isbadquery (q)) {//has not been queried, and is not a query that does not meet the criteria after the query        That.currentrequest = $.ajax ({//no cache reads data through Ajax Url:serviceurl, Data:data, Type:options.type, DataType:options.dataType}). Done (function (data                    ) {that.currentrequest = null;                That.processresponse (data, q, CacheKey);//Cache Options.onSearchComplete.call (that.element, q);  }). Fail (function (JQXHR, textstatus, Errorthrown) {options.onSearchError.call (that.element, Q,                JQXHR, Textstatus, Errorthrown);            }); }        }

You can see the core is the same as the above, but the key to the cache data becomes the Ajax URL and the parameters passed