1.1 连接两个或多个字符串
```
var string1 = "this is a ";
var string2 = "test";
var string2 = string1 + string2;
```
1.2 连接字符串和另一种数据类型
```
var numValue = 23.45;
var total = "and the total is" + numValue;
```
1.3 条件比较字符串
```
var strName = prompt("what's your name?","");
if(strName == "shelley"){
alert("your name is shelley!good for you");
}else{
alert("your name isn't shelley.bummer");
}
//运算符 说明示例
//相等 ==
//严格相等 ===
//不相等 !=
//严格不相等 !==
//大于 >
//大于或等于 >=
//小于 <
//小于或等于 <=
```
1.4 在字符串中查找子字符串
```
var testValue = "this is the cookbook's test string";
var subsValue = "cookbook";
var iValue = testValue.indexOf(subsValue);
```
返回一个数字，表示子字符串的第一个字符的索引或者位置，0表示字符串的第一个字符的索引位置。如果返回-1，那么表示没有找到子字符串
1.5 从一个字符串提取子字符串
```
var sentence = "this is one sentence.this is a sentence with a list of items:cherries,oranges,apples,bananas.";
var start = sentence.indexOf(":");
var end = sentence.indexOf(".",start);
var list = sentence.substring(start+1,end);
```
1.6 检查一个存在的、非空的字符串
```
if(((typeof unknownVariable != "undefined") && (typeof unknownVariable.valueOf() == "string")) && (unknownVariable.length > 0)){
alert("is true");
}
```
1.7 将一个关键字字符串分解为单独的关键字
```
<script>
window.onload = function(){
var keywordList = prompt("Enter keywords,separated by commas","");
var arrayList = keywordList.split(",");
var resultString = "";
for(var i = 0;i < arrayList.length;i++){
resultString += "keyword:" + arrayList[i] + "<br />";
}
var blk = document.getElementById("result");
blk.innerHTML = resultString;
}
</script>
<div id="result"></div>
```
1.8 插入特殊字符
```
<div id="result"></div>
<script>
var resultString = "this page shelley powers";
var blk = document.getElementById("result");
blk.innerHTML = resultString;
// 序列 字符
// \' 单引号
// \" 双引号
// \\ 反斜杠
// \b 退格
// \f 换页符
// \n 换行
// \r 回车
// \t 水平制表符
// \ddd 八进制序列
// \xdd 十六进制序列
// \uddd Unicode序列
</script>
```
1.9 处理textarea的单个行
```
<textarea>123</textarea>
<div id="result"></div>
<input id="inputbox" value="456">
<script>
var txtBox = document.getElementById("inputbox");
var lines = txtBox.value.split("\n");
var blk = document.getElementById("result");
blk.innerHTML = lines[lines.length-1];
</script>
```
1.10 去除字符串末尾的空白
```
<div id="test"></div>
<script>
var txtBox = document.getElementById("test"):
var lines = txtBox.value.split("\n");
var resultString = "";
for(var i = 0;i < lines.length;i++){
var string = lines[i].trim();
resultString += string + "-";
}
alert(resultString);
</script>
```
1.11 左补充或右补充一个字符串
```
<div id="result"></div>
<script>
var preflinelength = 20;
var oldStr = "this is a string";
var diff = preflinelength - oldStr.length;
var filer = "&nbps;";
for(var i = 0;i < diff;i++){
oldStr = filer + oldStr;
}
document.getElementById("result").innerHTML = oldStr;
</script>
```
