Javascript基础知识测试
一个Javascript基础知识测试,涉及的都是一些最基础的Javascript知识,测试一下,看看你能不能拿满分?
//请先写出以下代码中问号处的答案,再运行比较!
var a=0,b=0,c=0; a+++b+++c; alert([a,b,c]);//?
var a=[]; alert(a[a++]);//? alert(a);//?
var o={a:o++}; alert(o.a);//?
var f=function(){}; alert(f(f++));
alert(typeof(NaN))//?
alert(typeof(Infinity))//?
alert(typeof(null))//?
alert(typeof(undefined))//?
alert(NaN == NaN)//?
alert(NaN != NaN)//?
alert(NaN >= NaN)//?
alert(null == undefined)//?
alert(null >= undefined)//?
alert(null <= undefined)//? alert(parseInt("123abc"))//? alert(("123abc" - 0))//? alert(Infinity > 10)//?
alert(Infinity > "abc")//?
alert(Infinity == NaN)//?
alert(true == 1)//?
alert(new String("abc") == "abc")//?
alert(new String("abc") === "abc")//?
var a = "123abc"; alert(typeof(a++));//? alert(a);//?
var a = "123abc"; a.valueOf = function(){return parseInt(a);} alert(++a);//? alert(a-0);//?
var a = new Object(); a.toString = function(){return "123abc";} a.valueOf = function(){return parseInt(a);} alert(++a);//? alert(a-0);//?
var spv = String.prototype.valueOf; String.prototype.valueOf = function(){ return parseFloat(this); } alert("123abc" > 122);//? alert(new String("123abc") > 122);//? String.prototype.valueOf = spv;
var s = new String("abc"); alert(typeof(s) == typeof("abc"));//? alert(s === "abc");//? alert(s.toString() == s);//?
var a = new Object(),b = new Object(); a.toString = function(){return "a"}; b.toString = function(){return "b"}; alert(a>b);//? a.valueOf = function(){return 1}; b.valueOf = function(){return 0}; alert(a>b);//?
var step = function(a){ return function(x){ return x + a++; } } var a = step(10); var b = step(20); alert(a(10));//? alert(b(10));//?
我在评论一次
挺好的,真的很不错
吐血了,太菜了,基本功太差
呃~~~ 居然有几题做错了,看来基础太不扎实了-_-!!!