1.二维数组变为一维数组
function double_to_one() { collection = [1,[2],[3,4]] var array = []; for(var i = 0;i< collection.length;i++){ var new_array = collection[i]; if( new_array instanceof Array == true ){ for(var j = 0;j< new_array.length;j++){ array.push(new_array[j]); } } else{ array.push(new_array); } } return array; } // array = [1,2,3,4]
2.数组排序
从大到小 var rank_asc = function(){ var collection = [2,4,1,6,5,3] var array = collection.sort(); array = array.reverse(); return array; }; //array = [6,5,4,3,2,1] 从小到大 var rank_asc = function(collection){ var collection = [1,4,2,6,3,5] var array = collection.sort(); return array; }; // array = [1,2,3,4,5,6]
3,给出的数组,按照给定结果输出
function count_same_elements_3(collection){ var collection = var collection = [ "a", "a", "a", "e", "e", "e", "e", "e", "e", "e", "h", "h", "h", "h", "h", "h", "h[3]", "h", "h", "t", "t-2", "t", "t", "t", "t", "t", "t", "t[10]", "f", "f", "f", "f", "f", "f", "f", "f", "f", "c:8", "g", "g", "g", "g", "g", "g", "g", "b", "b", "b", "b", "b", "b", "d-5" ]; var result = []; var new_array = []; var length = collection.length; for(var i = 0;i < length; i++){ for(var j = i+1; j < length; j++){ if(collection[i] === collection[j]){ j = ++i; } } new_array.push(collection[i]); } // 去重复 for(var i=0;i<new_array.length;i++){ var number = 0; var temp = new_array[i]; var position = temp.indexOf('-');// '-'存在位置 var positions = temp.indexOf(':'); var positionss = temp.indexOf('['); if(position != -1 ){ //-1就是表示有对应的特殊符号(‘-’) number = parseFloat(temp.substr(position + 1));//截取字符串 temp = temp.substr(0,position); } else if(positions != -1){ number = parseFloat(temp.substr(positions + 1)); temp = temp.substr(0,positions); } else if(positionss != -1){ number = parseFloat(temp.substr(positionss + 1)); temp = temp.substr(0,positionss); } else{ for(var j = 0; j < collection.length; j++){ if(collection[j] == temp){ number++; } } } var k = {name: temp, summary: number}; if(result.length == 0){ result.push(k); } else { for (var n = 0, len = result.length; n < len; n++) { if (k.name == result[n].name) { result[n].summary += k.summary; } else if(k.name !== result[n].name && n == len -1){ //这是直到数组的最后一个 result.push(k); } } } number = 0; } return result; } // 预先给定的输出结果 result = [ {name: "a", summary: 3}, {name: "e", summary: 7}, {name: "h", summary: 11}, {name: "t", summary: 19}, {name: "f", summary: 9}, {name: "c", summary: 8}, {name: "g", summary: 7}, {name: "b", summary: 6}, {name: "d", summary: 5} ]
4.小数取整
1.丢弃小数部分,保留整数部分 parseInt(5/2) // 2 parseInt(7/4) //1 2.向上取整,有小数就整数部分加1 Math.cell(5/3) // 2 Math.ceil(5/2) //3 3,四舍五入. Math.round(5/2) //3 4,向下取整 Math.floor(5/3) //1 Math.floor(5/2) //2