JavaScript实现从数组中选出和等于固定值的n个数

function getCombBySum(array,sum,tolerance,targetCount){var util = {/*get combination from arrayarr: target arraynum: combination item lengthreturn: one array that contain combination arrays*/getCombination: function(arr, num) {var r=[];(function f(t,a,n){if (n==0){return r.push(t);}for (var i=0,l=a.length; i<=l-n; i++){f(t.concat(a[i]), a.slice(i+1), n-1);}})([],arr,num);return r;},//take array index to a arraygetArrayIndex: function(array) {var i = 0,r = [];for(i = 0;i<array.length;i++){r.push(i);}return r;}},logic = {//sort the array,then get what's we needinit: function(array,sum) {//clone arrayvar _array = array.concat(),r = [],i = 0;//sort by asc_array.sort(function(a,b){return a - b;});//get all number when it's less than or equal sumfor(i = 0;i<_array.length;i++){if(_array[i]<=sum){r.push(_array[i]);}else{break;}}return r;},//important functioncore: function(array,sum,arrayIndex,count,r){var i = 0,k = 0,combArray = [],_sum = 0,_cca = [],_cache = [];if(count == _returnMark){return;}//get current count combinationcombArray = util.getCombination(arrayIndex,count);for(i = 0;i<combArray.length;i++){_cca = combArray[i];_sum = 0;_cache = [];//calculate the sum from combinationfor(k = 0;k<_cca.length;k++){_sum += array[_cca[k]];_cache.push(array[_cca[k]]);}if(Math.abs(_sum-sum) <= _tolerance){r.push(_cache);} }logic.core(array,sum,arrayIndex,count-1,r);}},r = [],_array = [],_targetCount = 0,_tolerance = 0,_returnMark = 0;//check data_targetCount = targetCount || _targetCount;_tolerance = tolerance || _tolerance;_array = logic.init(array,sum);if(_targetCount){_returnMark = _targetCount-1;}logic.core(_array,sum,util.getArrayIndex(_array),(_targetCount || _array.length),r);return r;}