Home >Web Front-end >JS Tutorial >Part 1 Quick Start—Date, Math, and Global objects in js basic practice
Part 1 Quick Start—Date, Math, and Global objects in js basic practice
- php是最好的语言Original
- 2018-07-28 10:41:461654browse
tool.js
function print(str){
document.write(str);
}
function println(str){
document.write(str+"<br/>");
}
///////通过prototype属性扩展js API的对象的功能/////////
//※把trim方法融入到String对象中: str.trim()
String.prototype.trim = function(){
var start=0;//第一个非空格字符的位置
var end=this.length-1;//最后一个非空格字符的位置
while(start<=end && this.charAt(start)==' '){
start++;
}
while(start<=end && this.charAt(end)==' '){
end--;
}
return this.substring(start,end+1);
};
//给String对象添加一个toCharArray()方法
String.prototype.toCharArray = function(){
var chs=[];
for(var x=0;x<this.length;x++){
chs[x]=this.charAt(x);
}
return chs;
};
//给String对象添加一个reverse()方法
String.prototype.reverse = function(){
//函数内部可以再定义函数----Java做不到
function swap(arr,start,end){
var temp=arr[start];
arr[start]= arr[end];
arr[end] = temp;
}
var arr = this.toCharArray();
for(var start=0,end=arr.length-1; start<end; start++,end--){
swap(arr,start,end);
}
return arr.join("");
};
String.prototype.compareTo=function(str){
if(typeof(str)!="string"){
return 1;
}
var len1=this.length;
var len2=str.length;
var shortLen=len1>len2?len2:len1;
var longLen=len1>len2?len1:len2;
for(var i=0; i<shortLen; i++){
if(this.charAt(i)!=str.charAt(i)){
return this.charAt(i)-str.charAt(i);
}
}
if(len1>len2){
return 1;
}else if(len1<len2){
return -1;
}else{
return 0;
}
};
//为数组对象的shift()和unshift()函数取两个我们习惯的别名
Array.prototype.removeFirst=function(){
return this.shift();
};
Array.prototype.addFirst=function(e){
return this.unshift(e);
};
Array.prototype.addLast=function(e){
return this.push(e);
};Objects in JS language--Date object
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>JS语言中的对象--Date对象</title>
<script type="text/javascript" src="tools.js"></script>
</head>
<body>
<script type="text/javascript">
var date = new Date();
println(date);//date.toString()
println(date.toDateString());//只显示日期
println(date.toLocaleString());//本地格式
println(date.toLocaleDateString());//本地格式:只显示日期
var year = date.getYear(); //建议使用getFullYear()代替
println(year); //118 = 2018-1900
year = date.getFullYear();//※
println(year);
var month = date.getMonth();//※ 0~11 我们用时要 +1
println(month);
var day1 = date.getDay(); //※星期几, 其中星期日是0
var day2 = date.getDate(); //※月份中的第几天，就是我们平时用的“日期”
println(year + "." + (month + 1) + "." + day2);
</script>
<hr/>
<script type="text/javascript">
//格式转换
//日期对象 和 毫秒值之间的转换
var date2 = new Date();
var time = date2.getTime(); //日期对象 毫秒值
println("毫秒值:" + time);
time = time + 2 * 24 * 60 * 60 * 1000;//2天后
var date3 = new Date(time); //也可以用setTime() // 毫秒值 日期对象
println("后天:" + date3.toLocaleString());
//日期对象 和 字符串之间的转换
var str = date3.toLocaleString();//日期对象 字符串
//字符串 日期对象
//var str = "6/27/2018"; //格式 OK
//var str = "July 23, 2018"; //格式 OK
//var str = "2010/08/08"; //格式 OK
var str = "2010-08-08"; //格式 OK
var time = Date.parse(str);
var d = new Date(time);
println(d.toLocaleString());
</script>
<hr/>
<script type="text/javascript">
/*一个小语法:
with(对象){
//在该区域内可以直接使用"对象"的内容(属性和方法),不需要“对象.”
}
*/
var date=new Date();
with (date) {
var year = getFullYear();
var month = getMonth() + 1;
var day = getDate();
println(">>> " + year + "年" + month + "月" + day + "日");
}
</script>
</body>
</html>Objects in JS language- -Math object
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>JS语言中的对象--Math对象</title>
<script type="text/javascript" src="tools.js"></script>
</head>
<body>
<script type="text/javascript">
var x = -323.78;
x = Math.abs(x);
println("x=" + x);
x = 7.89;
x = Math.floor(x);
println(x);//8
x = Math.ceil(x);
println(x);//7
x = Math.exp(x);
println(x);//e^2
y = 5;
println(Math.pow(x, y)); //x 的 y 次幂
//round(x) 四舍五入
println(Math.round(4.56));
//random() 返回 0 ~ 1 之间的随机小数。
//生成10个[1,10]范围内的随机整数
for(var i=1;i<=10;i++){
//int n = (int)(Math.random()*10) +1; //Java写法
//var n = Math.floor( Math.random()*10 ) +1; //JS写法1---用Math.floor()实现取整
var n=parseInt(Math.random()*10)+1;//JS写法2---用parseInt()实现取整
print(n+" ");
}
println("");
</script>
</body>
</html>Objects in JS language--Global object, top-level function (global function)
js puts some common functions It is defined in an object called Global, and "Global." cannot be written when calling.
eval(str): Treat the string as a js statement to evaluate and execute
Number(s): Convert the parameter s into "Value (value of type Number)", if the parameter is a Date, the millisecond value is returned. If the parameter cannot be converted into a value, it is returned: NaN
parseFloat(): Parse a string and Returns a floating point number.
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>JS语言中的对象--Global对象, 顶层函数（全局函数）</title>
<script type="text/javascript" src="tools.js"></script>
</head>
<body>
<script type="text/javascript">
//js把一些通用的函数定义在一个叫Global的对象中，调用时不能写"Global."
//eval(str): 把字符串当成js语句来进行评估且执行
eval("x=10;y=20;document.write(x*y);");
document.write("<br/>" + eval("2+2") + "<br/>");
var x = 10;
document.write(eval(x + 17) + "<br/>");
//isNaN(s): 判断s是否是一个"非Number类型"的值
var str = "123";
println(isNaN(str)); //false ---不是"非Number类型"
str = "abc123";
println(isNaN(str)); //true ---是"非Number类型"
</script>
<hr />
<script type="text/javascript">
//Number(s): 把参数s转换成"数值(Number类型的值)",如果参数是Date则返回毫秒值，如果参数不能转换成数值则返回: NaN
var test1 = new Boolean(true);
var test2 = new Boolean(false);
var test3 = new Date();
var test4 = new String("999");
var test5 = new String("999 888");
document.write(Number(test1) + "<br />");
document.write(Number(test2) + "<br />");
document.write(Number(test3) + "<br />");
document.write(Number(test4) + "<br />");
document.write(Number(test5) + "<br />");
document.write(Number.MAX_VALUE + "<br />");
document.write(Number.MIN_VALUE + "<br />");
document.write(Number.NEGATIVE_INFINITY + "<br />");
</script>
<hr />
<script type="text/javascript">
//parseFloat(): 解析一个字符串并返回一个浮点数。
var str = "3.14159";
var val = parseFloat(str);
val *= 2;
println(val);
//parseInt(): 解析一个字符串，并返回一个整数。
//parseInt(str, radix) : 没有参数radix时为十进制
//将字符串 十进制数
var num = parseInt("110", 10); //10进制的字符串"110" 110
println(num);//110
var num = parseInt("110", 2); //2进制的字符串"110" --> 6
println(num);//6
var num = parseInt("110", 16); //16进制的字符串"110" --> 272
println(num);//272
//将十进制数 --> 其它进制格式的字符串
var num = 100; //js自动会把一个数值包装成一个Number对象
//NumberObject.toString(radix)
println(num.toString(2)); //把num转换成2进制的字符串
println(num.toString(16)); //把num转换成16进制的字符串
</script>
</body>
</html>Related articles:
Part 2 Quick Start—JS Basics Practical BOM--Browser Object Model, DOM
Part 3 Quick Start—JS Basic Practical Application Code Sharing
Related Videos:
27 Classic Practical Video Tutorials for Front-end JS Development-Free Online Video Tutorial
The above is the detailed content of Part 1 Quick Start—Date, Math, and Global objects in js basic practice. For more information, please follow other related articles on the PHP Chinese website!
Statement：
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn
Previous article：Part 2 Quick Start - JS Basics Practical BOM - Browser Object Model, DOMNext article：Part 2 Quick Start - JS Basics Practical BOM - Browser Object Model, DOM
Related articles
See more- An in-depth analysis of the Bootstrap list group component
- Detailed explanation of JavaScript function currying
- Complete example of JS password generation and strength detection (with demo source code download)
- Angularjs integrates WeChat UI (weui)
- How to quickly switch between Traditional Chinese and Simplified Chinese with JavaScript and the trick for websites to support switching between Simplified and Traditional Chinese_javascript skills