一些javascript题目

var result = [10] + 1;

console.log(result)

show sourceview sourceprint?

"101"

存在运算符"+"，意味着将[10]转化为一个值，相当于调用其valueOf()方法，而Array的valueOf相当于其toString

var result = ['a', 'b', 'c'] + "";

console.log(result)

show sourceview sourceprint?

"a,b,c"

与一个空字符相加，我们大可以就当成强行调用其toString方法，而Array的toString方法相当于调用其join方法，join的默认分隔符则为","

var result = 'a' + 5;

console.log(result)

show sourceview sourceprint?

"a5"

加号表达式优先考虑字符串拼接

var result = 3.75 | 0;

console.log(result)

show sourceview sourceprint?

3

数值|0相当于对数值进行Math.floor

var result = 65 / 'a';

console.log(result)

show sourceview sourceprint?

NaN

'a'首先要转换为一个Number类型,既然不能转换为一个正常的数字,就转换为NaN,与NaN进行运算结果都为NaN

var obj = {"10": 1};

obj[10] = 2;

obj[[1, 0]] = 3;

var result = obj["10"] + obj[10] + obj[[1, 0]];

console.log(result)

show sourceview sourceprint?

7

对象的键总为字符串,因此obj[10]相当于obj["10"],obj[[1,0]]相当于obj["1,0"]

var $ = {"": String};

var result = !!$[([])]();

console.log(result)

show sourceview sourceprint?

false

转换过程如下

!!$[([])]() -->  !!$[""]() --> !!String() --> !!"" --> false

var result = (' \t\r\n ' == 0);

console.log(result)

show sourceview sourceprint?

true

考空白字符串的类型

参见http://www.cnblogs.com/rubylouvre/archive/2009/09/18/1568794.html这里的回复讨论

var a = new String("123");

var b = "123";

var result = (a === b);

console.log(result)

show sourceview sourceprint?

false

一个为object一个为string

var a = {key: 1};

var b = {key: 1};

var result = (a == b);

console.log(result)

show sourceview sourceprint?

false

两个对象总是不等的

http://blog.vjeux.com/2009/javascript/smallhash-information-compression.html

标签: javascript