//生成大写字母 A的Unicode值为65
function generateBig_1(){
 var str = [];
 for(var i=65;i<91;i++){
  str.push(String.fromCharCode(i));
 }
 return str;
}
//生成大写字母 a的Unicode值为97
function generateSmall_1(){
 var str = [];
 for(var i=97;i<123;i++){
  str.push(String.fromCharCode(i));
 }
 return str;
}
//将字符串转换成Unicode码
function toUnicode(str){
 var codes = [];
 for(var i=0;i<str.length;i++){
  codes.push(str.charCodeAt(i));
 }
 return codes;
}
 
function generateSmall(){
 var ch_small = 'a';
 var str_small = '';
 for(var i=0;i<26;i++){
  str_small += String.fromCharCode(ch_small.charCodeAt(0)+i);
 }
 return str_small;
}
 
function generateBig(){
 var ch_big = 'A';
 var str_big = '';
 for(var i=0;i<26;i++){
  str_big += String.fromCharCode(ch_big.charCodeAt(0)+i);
 }
 return str_big;
}
 
console.log(generateBig());
console.log(generateSmall());
 
console.log(toUnicode(generateBig()));
console.log(toUnicode(generateSmall()));
 
console.log(generateBig_1());
console.log(generateSmall_1());

function getCharacter(flag){ 
 var character=""; 
 if(flag==="lower"){ 
 character = String.fromCharCode(Math.floor(Math.random()*26)+"a".charCodeAt(0)); 
 } 
 if(flag==="upper"){ 
 character = String.fromCharCode(Math.floor(Math.random()*26)+"A".charCodeAt(0)); 
 } 
 return character; 
} 
function getUpperCharacter(){ 
 return getCharacter("upper");; 
}
function getLowerCharacter(){ 
 return getCharacter("lower");; 
} 
console.log(getUpperCharacter());
console.log(getLowerCharacter());

/** 
* 返回一个随机的小写字母 
*/ 
function getLowerCharacter(){ 
return getCharacter("lower");; 
} 


/** 
* 返回一个随机的大写字母 
*/ 
function getUpperCharacter(){ 
return getCharacter("upper");; 
} 


/** 
* 返回一个字母 
*/ 
function getCharacter(flag){ 
var character = ""; 
if(flag === "lower"){ 
character = String.fromCharCode(Math.floor( Math.random() * 26) + "a".charCodeAt(0)); 
} 
if(flag === "upper"){ 
character = String.fromCharCode(Math.floor( Math.random() * 26) + "A".charCodeAt(0)); 
} 
return character; 
}