JavaScript 数据类型总结

概述

ECMAScript中有5种简单数据类型：Undefined,Null,Boolean,Number和String。还有一种复杂数据类型–Object

typeof操作符
由于Javascript中的变量是松散类型的，所以它提供了一种检测当前变量的数据类型的方法，也就是typeof关键字，在上面提到的ECMAScript中的5种简单数据类型中，（记住，这5种只是数据类型，代表一种数据类型，就想C#中的int，string类型一样），通过typeof关键字，对这5种数据类型会返回下面的值（以字符串形式显示

“undefined” ———- 如果值未定义 Undefined

“boolean” ———- 如果这个值是布尔值 Boolean

“string” ———- 如果这个值是字符串 String

“number” ———- 如果这个值是数值类型 Number

“object” ———- 如果这个值是对象或null Object

“function” ———- 如果这个值是函数 Function

不过严格来说，函数在ECMAScript中是对象，每个函数都是Function这个类的一个实例，既然函数是一个对象，那么它也就是一个引用类型了，所以一个函数只是一个变量名而已，因此，在很多场合常常可以看到，将函数名作为参数，传进函数中，然后进行调用，这就类似于C#中的委托，在后面会详细的讲解函数这个东西，毕竟Javascript中很多东西都依赖于函数来实现。

由以上操作可知 Array 属于 Obejct

常用类型操作示例

1 Array

var multipleValues = [];multipleValues[0] = 50;multipleValues[2] = "Music"var = multipleValues = [50,60,"Mouse"];console.log(multipleValues.length); //get the length of the arrayarrays are objectsvar multipleValues = []; //the syntax to creating array数组的方法someFunction(params); //to call a function//methods are functions that belong to a methodsomeObject.someMethod(); //to call a methodvar multipleValues = [10,20,30,40,50];var reversedValues = multipleValues.reverse();array.join(); //return a stringarray.sort(); //return a sorted array

2 NUMBERS

var x = 200;//javascript numbers are 64-bit floating point numbers.addition vs concatenationvar foo=5;var bar=5;console.log(foo + bar) //10var foo=5;var bar="5";console.log(foo + bar); // 55 - one is a stringvar foo = 5;var bar = "b"console.log(foo * bar) //NaN which means not a NUMBERSNOT A NUMBER将字符串装换成数字var foo="55";var myNumber = Number(foo); //make it a Numberif (isNaN(myNumber)){    console.log("It's not a number!");}//double negative -if NOT NOT a numberif(! isNaN(myNumber)){    console.log("It IS a number");}USING THE MATH OBJECTvar x = 200.6;var y = Math.round(x);var a = 200, b = 10000, c = 4;var beggest = Math.max(a,b,c);var smallest = Math.min(a,b,c);Math.PI Math.random() .sqrt() .log() and so on ....

3 STRING

quotes inside quotes 转义符号的使用\ " ' ";Properties:str.lengthstr.toUpperCase()Method:split("delimiter");var phrase = "we want a groovy keyrowd.";var position = phrase.indexOf("groovy"); // 10//it return s -1 if the term is not foundif (phrase.indexOf("DDDD") == -1){    console.log("That word does not occur");}// there is also .lastIndexOf()var phrase = "yet another phrase.";var segment = phrase.slice(6,5);.substring() .substr()STRING COMPARISONvar str1 = "Hello";var str2 = "hello";//str1 != str2if(str1.toLowerCase() == str2){    console.log("Yes equal ");}

4 DATE

var today = new Date(); //current date and timevar y2k new Date(2000,0,1); //year, month(sero based), dayvar y2k = new Date(2000,0,1,0,0,0);//y,m.d,h,m,stoday.getMonth(); //return 0-11today.getFullYear()//yyyy( not sero-based)today.getYear(); //deprecatedtoday.getDate(); //1-31 day of monthtoday.getDay(); // 0-6 day of week. 0 == sundaytoday.getHours(); //0-23today.getTime(); //milliseconds since 1/1/1970today.setMnoth(5);today.setFullYear(2012);today.setFullYear(2012);today.setDay(0);//etc.var date1 = new Date(2000,0,1);var date2 = new Date(2000,0,1);date1 == date2 //falsedate1.getTime() == date2.getTime(); //true

5 Object

//way1var player = new Object();player.name = "Fred";player.score = 10000;player.rank = 1;//way2var player = {name: "Fred", score: 10000, rank:1};function playerDetails(){    //display kinformation about each player    console.log(this.name + "has rank of:" + this.rank +    "and a score of " + this.score);}player1.logDetails = playerDetails;player2.logDetails = playerDetails;player1.logDetails();player2.logDetails();

相关概念参考写得极好

http://www.cnblogs.com/top5/archive/2012/03/20/2408330.html