javascript 常用方法

javascript常用方法:

(1)startWith

js本身没有startWith方法,我进行了如下封装:

String.prototype.startWith=function (string)
{
    return (this.indexOf(string)==0);
}
var aaaa="/c/c";
alert(aaaa.startWith('/'));

 

(2)计算md5值

js文件:calcMd5.js

/*
 * A JavaScript implementation of the RSA Data Security, Inc. MD5 Message
 * Digest Algorithm, as defined in RFC 1321.
 * Copyright (C) Paul Johnston 1999 - 2000.
 * Updated by Greg Holt 2000 - 2001.
 * See http://pajhome.org.uk/site/legal.html for details.
 */

/*
 * Convert a 32-bit number to a hex string with ls-byte first
 */
var hex_chr = "0123456789abcdef";
function rhex(num)
{
  str = "";
  for(j = 0; j <= 3; j++)
    str += hex_chr.charAt((num >> (j * 8 + 4)) & 0x0F) +
           hex_chr.charAt((num >> (j * 8)) & 0x0F);
  return str;
}

/*
 * Convert a string to a sequence of 16-word blocks, stored as an array.
 * Append padding bits and the length, as described in the MD5 standard.
 */
function str2blks_MD5(str)
{
  nblk = ((str.length + 8) >> 6) + 1;
  blks = new Array(nblk * 16);
  for(i = 0; i < nblk * 16; i++) blks[i] = 0;
  for(i = 0; i < str.length; i++)
    blks[i >> 2] |= str.charCodeAt(i) << ((i % 4) * 8);
  blks[i >> 2] |= 0x80 << ((i % 4) * 8);
  blks[nblk * 16 - 2] = str.length * 8;
  return blks;
}

/*
 * Add integers, wrapping at 2^32. This uses 16-bit operations internally 
 * to work around bugs in some JS interpreters.
 */
function add(x, y)
{
  var lsw = (x & 0xFFFF) + (y & 0xFFFF);
  var msw = (x >> 16) + (y >> 16) + (lsw >> 16);
  return (msw << 16) | (lsw & 0xFFFF);
}

/*
 * Bitwise rotate a 32-bit number to the left
 */
function rol(num, cnt)
{
  return (num << cnt) | (num >>> (32 - cnt));
}

/*
 * These functions implement the basic operation for each round of the
 * algorithm.
 */
function cmn(q, a, b, x, s, t)
{
  return add(rol(add(add(a, q), add(x, t)), s), b);
}
function ff(a, b, c, d, x, s, t)
{
  return cmn((b & c) | ((~b) & d), a, b, x, s, t);
}
function gg(a, b, c, d, x, s, t)
{
  return cmn((b & d) | (c & (~d)), a, b, x, s, t);
}
function hh(a, b, c, d, x, s, t)
{
  return cmn(b ^ c ^ d, a, b, x, s, t);
}
function ii(a, b, c, d, x, s, t)
{
  return cmn(c ^ (b | (~d)), a, b, x, s, t);
}

/*
 * Take a string and return the hex representation of its MD5.
 */
function calcMD5(str)
{
  x = str2blks_MD5(str);
  a =  1732584193;
  b = -271733879;
  c = -1732584194;
  d =  271733878;

  for(i = 0; i < x.length; i += 16)
  {
    olda = a;
    oldb = b;
    oldc = c;
    oldd = d;

    a = ff(a, b, c, d, x[i+ 0], 7 , -680876936);
    d = ff(d, a, b, c, x[i+ 1], 12, -389564586);
    c = ff(c, d, a, b, x[i+ 2], 17,  606105819);
    b = ff(b, c, d, a, x[i+ 3], 22, -1044525330);
    a = ff(a, b, c, d, x[i+ 4], 7 , -176418897);
    d = ff(d, a, b, c, x[i+ 5], 12,  1200080426);
    c = ff(c, d, a, b, x[i+ 6], 17, -1473231341);
    b = ff(b, c, d, a, x[i+ 7], 22, -45705983);
    a = ff(a, b, c, d, x[i+ 8], 7 ,  1770035416);
    d = ff(d, a, b, c, x[i+ 9], 12, -1958414417);
    c = ff(c, d, a, b, x[i+10], 17, -42063);
    b = ff(b, c, d, a, x[i+11], 22, -1990404162);
    a = ff(a, b, c, d, x[i+12], 7 ,  1804603682);
    d = ff(d, a, b, c, x[i+13], 12, -40341101);
    c = ff(c, d, a, b, x[i+14], 17, -1502002290);
    b = ff(b, c, d, a, x[i+15], 22,  1236535329);    

    a = gg(a, b, c, d, x[i+ 1], 5 , -165796510);
    d = gg(d, a, b, c, x[i+ 6], 9 , -1069501632);
    c = gg(c, d, a, b, x[i+11], 14,  643717713);
    b = gg(b, c, d, a, x[i+ 0], 20, -373897302);
    a = gg(a, b, c, d, x[i+ 5], 5 , -701558691);
    d = gg(d, a, b, c, x[i+10], 9 ,  38016083);
    c = gg(c, d, a, b, x[i+15], 14, -660478335);
    b = gg(b, c, d, a, x[i+ 4], 20, -405537848);
    a = gg(a, b, c, d, x[i+ 9], 5 ,  568446438);
    d = gg(d, a, b, c, x[i+14], 9 , -1019803690);
    c = gg(c, d, a, b, x[i+ 3], 14, -187363961);
    b = gg(b, c, d, a, x[i+ 8], 20,  1163531501);
    a = gg(a, b, c, d, x[i+13], 5 , -1444681467);
    d = gg(d, a, b, c, x[i+ 2], 9 , -51403784);
    c = gg(c, d, a, b, x[i+ 7], 14,  1735328473);
    b = gg(b, c, d, a, x[i+12], 20, -1926607734);
    
    a = hh(a, b, c, d, x[i+ 5], 4 , -378558);
    d = hh(d, a, b, c, x[i+ 8], 11, -2022574463);
    c = hh(c, d, a, b, x[i+11], 16,  1839030562);
    b = hh(b, c, d, a, x[i+14], 23, -35309556);
    a = hh(a, b, c, d, x[i+ 1], 4 , -1530992060);
    d = hh(d, a, b, c, x[i+ 4], 11,  1272893353);
    c = hh(c, d, a, b, x[i+ 7], 16, -155497632);
    b = hh(b, c, d, a, x[i+10], 23, -1094730640);
    a = hh(a, b, c, d, x[i+13], 4 ,  681279174);
    d = hh(d, a, b, c, x[i+ 0], 11, -358537222);
    c = hh(c, d, a, b, x[i+ 3], 16, -722521979);
    b = hh(b, c, d, a, x[i+ 6], 23,  76029189);
    a = hh(a, b, c, d, x[i+ 9], 4 , -640364487);
    d = hh(d, a, b, c, x[i+12], 11, -421815835);
    c = hh(c, d, a, b, x[i+15], 16,  530742520);
    b = hh(b, c, d, a, x[i+ 2], 23, -995338651);

    a = ii(a, b, c, d, x[i+ 0], 6 , -198630844);
    d = ii(d, a, b, c, x[i+ 7], 10,  1126891415);
    c = ii(c, d, a, b, x[i+14], 15, -1416354905);
    b = ii(b, c, d, a, x[i+ 5], 21, -57434055);
    a = ii(a, b, c, d, x[i+12], 6 ,  1700485571);
    d = ii(d, a, b, c, x[i+ 3], 10, -1894986606);
    c = ii(c, d, a, b, x[i+10], 15, -1051523);
    b = ii(b, c, d, a, x[i+ 1], 21, -2054922799);
    a = ii(a, b, c, d, x[i+ 8], 6 ,  1873313359);
    d = ii(d, a, b, c, x[i+15], 10, -30611744);
    c = ii(c, d, a, b, x[i+ 6], 15, -1560198380);
    b = ii(b, c, d, a, x[i+13], 21,  1309151649);
    a = ii(a, b, c, d, x[i+ 4], 6 , -145523070);
    d = ii(d, a, b, c, x[i+11], 10, -1120210379);
    c = ii(c, d, a, b, x[i+ 2], 15,  718787259);
    b = ii(b, c, d, a, x[i+ 9], 21, -343485551);

    a = add(a, olda);
    b = add(b, oldb);
    c = add(c, oldc);
    d = add(d, oldd);
  }
  return rhex(a) + rhex(b) + rhex(c) + rhex(d);
}
 

 测试:

var result=calcMD5("whuang");

 

(3)把json对象转换为字符串

依赖的js文件见附件

范例:

var person={"name":"黄威","QQ":"1287789687"};
person= JSON.stringify(person);
alert(person)

 

 

 

(4)字符串出现的次数

var str = "goodsaa.name";

    var find = "x";

    var reg = new RegExp(find, "g");

    var c = str.match(reg);

    alert(c ? c.length : 0);

上例是求str中字符x 出现的次数。RegExp的第二个参数g 表示全局搜索。

 

(5)判断字符串中句号(不作为通配符)出现的次数

<script type="text/javascript">

    var str = "goodsaa..name";

    var find = "\\.";//对句点要转义

    var reg = new RegExp(find, "g");

    var c = str.match(reg);

    alert(c ? c.length : 0);

</script>

(6)把json字符串转化为json对象

var jsonStr='{"2":"1.2.3","3":"1.2.5"}';
var jsonObj2=eval("("+jsonStr+")");
alert(jsonObj2["2"])

 (7)js中获取年份

方式一:

 

IE	98年	99年	2000年	2001年			2012年
火狐	98年	99年	100年	101年			112年

在Firefox 里面getYear 返回的是"当前年份-1900" 的值(以前都如此) 

在IE里面当today的年份大于等于2000的时候直接把1900加上了 

var appName23=(navigator.appName);
var appCodeName32=navigator.appCodeName;
var isFirefox=(appName23=="Netscape")&&(appCodeName32=="Mozilla");
var today = new Date();
            var year = today.getYear();
			if(isFirefox){//browser is firefox
				year=year+1900;
				 alert("火狐: "+year);
			}else{////browser is IE
				year=year>1999?year:year+1900;
				 alert("IE: "+year);
			}
            

 方式二:

var today = new Date();

            var year = today.getFullYear();

           alert(year);

方式三:

var today = new Date();

            var year = today.getUTCFullYear();

           alert(year);

(8)document.all的兼容性

if(isFirefox){//browser is firefox

       oTable=document.getElementById(this.sTABLEID);

    }else{

       oTable=document.all[this.sTABLEID];

    }

nowtime.value = document.all.examclock.innerHTML;

结论:火狐不支持document.all,但是IE支持

(9)js动态添加组件

var buttonTd=com.whuang.hsj.$$id("buttonTd");//td tag
		var newInput =document.createElement("input");
		newInput.type="button"; 
		newInput.name="input1";
		newInput.value="修改密码";
		buttonTd.appendChild(newInput);

 (10)禁用表单提交事件

方式一:

event.returnValue= false;

方式二：

returnfalse;

 

event.returnValue在火狐中不好使，应该改为：

returnfalse;