Javascript数据结构算法之数组基础篇

数组

一个存储元素的线性集合。

1. 创建数组

var objects = [1, "joe", true, null];

isArray()
Array.isArray(objects);

2. 读写数组

数组的长度可以任意增长。

3. 由字符串生成数组

split()

var sentence = "the quick brown fox jumped over the lazy pig";
var words = sentence.split(" ");
for(var i = 0; i<words.length; i++)
{
    print("word"+i+":"+words[i]);
}

4. 查找元素

indexOf()
lastIndexOf()

var names=["David", "Cynthia", "Raymond", "Clayton", "Jennifer", "David"];
var name = "David";
var firstposition = names.indexOf(name);
var lastposition = names.lastIndexOf(name);
if(firstposition>=0)
{
    print("Found "+name+" at positon "+firstposition);
    if(lastposition>=0)
    print("Last found "+name+" at positon "+lastposition);
}
else
{
    print(name+"not found in array");
}

5. 数组的字符串表示

join()

var names=["David", "Cynthia", "Raymond", "Clayton", "Jennifer"]
print(names);
var namestr = names.join();
print(namestr);
namestr = names.toString();
print(namestr);

the results are the same: David,Cynthia,Raymond,Clayton,Mike,Jennifer

6. 由已有数组创建新数组

concat()
splice()

var cisDept = [1,2,3,4,5];
var dmpDept = [6,7,8];
var itDiv = cisDept.concat(dmpDept);
print(itDiv);
itDiv = dmpDept.concat(cisDept);
print(itDiv);

the results is:
1,2,3,4,5,6,7,8
6,7,8,1,2,3,4,5

var itDiv = [1,2,3,4,5,6,7,8];
var cisDept = itDiv.splice(3,3);
print(cisDept);
print(itDiv);

the results is:
4,5,6
1,2,3,7,8

7. 可变函数

push()
unshift()
pop()
shift()
reverse()
sort()

var nums = [3,4,5];
nums.push(6);
nums.unshift(1,2);
print(nums);
nums.reverse();
print(nums); 

var diso_nums = [3,1,2,100,4,200];
function compare(num1, num2){
    return num1 - num2;
}
diso_nums.sort(compare);
print(diso_nums);

the results are:
1,2,3,4,5,6
6,5,4,3,2,1
1,2,3,4,100,200

8. 迭代器方法

forEach()
every()
some()
reduce()
reduceRight()
：返回一个值，或者执行某个操作

function square(num){
    print(num, num*num);
}
function isEven(num){
    return num % 2 == 0;
}
function concat(accumulatedString, item){
    return accumulatedString + item;
}

var nums1 = [1,2,3,4,5];
var nums2 = [2,4,6,8,10];
var nums3 = [1,2,3,5,7];
var words = ["the ", "quick ", "brown ", "fox "];

nums1.forEach(square);//对数组中每个元素都是用Squre()方法
nums2.every(isEven); //true
nums3.some(isEven);  //true
words.reduce(concat);  //累加："the quick brown fox"
words.reduceRight(concat);  //反向累加："fox brown quick the"

map()
filter()
：返回一个数组

function curve(grade){
    return grade + 5;
}

var grades = [77, 65, 81, 92, 83];
var nums = [2,4,5,6,8,10];
var newgrades = grades.map(curve);
var evens = nums.filter(isEven);

function afterc(str){
    if(str.indexOf("cie") > -1 ){
        return true;
    }
    return false;
}

var words = ["recieve", "deceive", "percieve", "deceit", "concieve"];
var rightwords = words.filter(afterc);

9. 二维数组

10. 参差不齐的数组

11. 对象数组

function weekTemps(){
    this.dataStore = [];
    this.add = add;
    this.average = average;
}
function add(temp)
{
    this.dataStore.push(temp);
}
function average()
{
    var total;
    for(var i=0; i<this.dataStore.length; i++)
    {
        total += this.dataStore[i];
    }
    return total / this.dataStore.length;
}

var thisWeek = new weekTemps();
thisWeek.add(52);
thisWeek.add(62);
thisWeek.add(55);
thisWeek.add(61);
thisWeek.add(50);
thisWeek.add(49);
thisWeek.add(59);
print(thisWeek.average());