string = "first:10second:20last:30"

string = "first:10second:40last:30"

/***************************************************************************************************/
var str = "AA BB CC DD EE, AA BB CC DD EE";
str = str.replace("AA", "11");         //use substring as parameter, replace only the first match
alert('parameter use substring:\n' + str);
/*
output:

parameter use substring:
11 BB CC DD EE, AA BB CC DD EE
*/
/***************************************************************************************************/

str = "AA BB CC DD EE, AA BB CC DD EE";
str = str.replace(/DD/g, "22");      //use regular expression, set replace flag to global, then replace all match
alert('parameter use regex:\n' + str);
/*
output:

parameter use regex:
AA BB CC 22 EE, AA BB CC 22 EE
*/
/***************************************************************************************************/

str = "AA BB CC DD EE, AA BB CC DD EE";
//g = global search
str = str.replace(/DD/g, "22");      //replace all match
alert('regex with flag global:\n' + str);
/*
output:

regex with flag gloabl:
AA BB CC 22 EE, AA BB CC 22 EE
*/
/***************************************************************************************************/

str = "AA BB CC DD EE, AA BB CC DD EE";
//without global flag
str = str.replace(/DD/, "22");      //replace the first match only
alert('regex without flag global:\n' + str);
/*
output:

regex without flag global:
AA BB CC 22 EE, AA BB CC DD EE
*/
/***************************************************************************************************/

// i = ignore case
str = "AA BB CC DD EE, aa BB CC DD EE";
str = str.replace(/aa/gi, "Apple");
alert('regex with flag ignore case:\n' + str);
/*
output:

regex with flag ignore case:
Apple BB CC DD EE, Apple BB CC DD EE
*/
/***************************************************************************************************/
// ignore case is not set
str = "AA BB CC DD EE, aa BB CC DD EE";
str = str.replace(/aa/g, "Apple");
alert('regex without flag ignore case:\n' + str);
/*
output:

regex without flag ignore case:
AA BB CC DD EE, Apple BB CC DD EE
*/
/***************************************************************************************************/
//m = multi-line
str = "AA BB CC DD EE" +  "\n"  + "AA BB CC DD EE";
str = str.replace(/^AA/gm, "Apple");      //replace string which is beginning of 'AA'
alert('regex with flag multi-line:\n' + str);
/*
output:

regex with flag multi-line:
Apple BB CC DD EE
Apple BB CC DD EE
*/
/***************************************************************************************************/
//if multi-line is not set
str = "AA BB CC DD EE" +  "\n"  + "AA BB CC DD EE";
str = str.replace(/^AA/g, "Apple");
alert('regex without flag multi-line:\n' + str);

/*
output:

regex without flag multi-line:
Apple BB CC DD EE
AA BB CC DD EE
*/
/***************************************************************************************************/

var string = "first:10second:20last:30";

// 未知方法...
...............
...............
...............
// 把字串分割, 得到如下兩部份:
// string1 = "first:10second:";
// string2 = "last:30";

string = string1 + 40 + string2; // 與新數值合併

var s = "first:10second:20last:30";
var re = /^first:(\d+)second:(\d+)last:(\d+)$/;

var m = s.match(re);

if (m != null){     
   m[2] = 40;
   var str = "first:" + m[1] + "second:" + m[2] + "last:" + m[3];             
   alert(str);      //first:10second:40last:30
}

//regular expression 使用 g (global)後，string.match就不會傳回 submatch

var s = "first:10second:20last:30,first:40second:50last:60";

var re = /first:(\d+)second:(\d+)last:(\d+)/g;
var m = s.match(re);

if (m != null){
   alert('m[0]:' + m[0]);  //m[0]:first:10second:20last:30
   alert('m[1]:' + m[1]);  //m[1]:first:40second:50last:60
}

// 使用 regex.exec(string)例子，目的是取得regex submatch string

var s = "first:10second:20last:30,first:40second:50last:60";

var re = /first:(\d+)second:(\d+)last:(\d+)/g;
var m = re.exec(s);

if (m != null){
   alert(m[0]);  //first:10second:20last:30
   alert(m[1]);  //10
   alert(m[2]);  //20
   alert(m[3]);  //30
}

m = re.exec(s);   //注意這裡會從 Last match position開始找，而不是重頭開始找

if (m != null){
   alert(m[0]);  //first:40second:50last:60
   alert(m[1]);  //40
   alert(m[2]);  //50
   alert(m[3]);  //60
}

//example:
var s = "first:10second:20last:30,first:40second:50last:60";
var re = /(\d+)/g;

var f = function(x){
   x = parseInt(x);
   x = x + 10;
   return x;
};

s = s.replace(re, f);
alert(s);   //first:20second:30last:40,first:50second:60last:70