字符串:一系列字符的集合。用于存储和处理文本。
一般由单双引号括起来
可用索引位置访问每一个位置的字符
<script type="text/javascript">
//字面量声明字符串
var str="abcd";
//实例化,不建议(拖慢执行速度等问题)
var str1=new String("abcd");
//字符串长度
console.log(str.length);
//转义字符
console.log("双引号\"");
console.log("单引号\'");
console.log("换行a\n换行b");
console.log("回\r车");
console.log("tab\t制表符");
console.log("退\b格符");
console.log("换\f页符");
charAt() 返回指定索引位置的字符
<script type="text/javascript">
var str="aAbBcCdD123456";
//console.log(str.charAt(5));//C
</script>
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charCodeAt() 返回指定索引位置字符的 Unicode 值
<script type="text/javascript">
var str="aAbBcCdD123456";
//console.log(str.charCodeAt(5));//67
</script>
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concat() 连接两个或多个字符串,返回连接后的字符串
<script type="text/javascript">
var str="aAbBcCdD123456";
var a="1111111111111"
//console.log(str.concat(a));//aAbBcd12345611111111111
</script>
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fromCharCode() 将 Unicode 转换为字符串
<script type="text/javascript">
//console.log(String.fromCharCode(65,66,67,68,69));//ABCDE
</script>
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indexOf() 返回字符串中检索指定字符第一次出现的位置 没有是-1
<script type="text/javascript">
var str="aAbBcCdDaAbBcCdDaAbBcCdD";
//console.log(str.indexOf("c"));//4
</script>
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lastIndexOf() 返回字符串中检索指定字符最后一次出现的位置 没有是-1
<script type="text/javascript">
var str="aAbBcCdDaAbBcCdDaAbBcCdD";
//console.log(str.lastIndexOf("c"));//20
</script>
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split() 把字符串分割为子字符串数组
括号不写东西就是原字符串变成了数组 “”是单个字符分割 “x”是以x分割 首尾会形成空值
<script type="text/javascript">
var str="aAbBcCdDa123456";
/*console.log(str.split());//[aAbBcCdDa123456]
console.log(str.split(""));//["a", "A", "b", "B", "c", "C", "d", "D", "a", "1", "2", "3", "4", "5", "6"]
console.log(str.split("a"));*/[“”,”AbBcCdD”,”123456”]
</script>
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substr() 从起始索引号提取字符串中指定数目的字符
从a位置取x个
<script type="text/javascript">
var str="aAbBcCdDa123456";
console.log(str.substr(4,4));//cCdD
</script>
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slice() 提取字符串的片断,并在新的字符串中返回被提取的部分
从a位置到b位置 不包含b 只写一个默认拉到最后
<script type="text/javascript">
var str="aAbBcCdDa123456";
console.log(str.slice(4,8));//cCdD
console.log(str.slice(8,4));//空
console.log(str.slice(8));//a123456
</script>
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substring() 提取字符串中两个指定的索引号之间的字符
部分正负 从小的开始 到大的结束 不包括大的
<script type="text/javascript">
var str="aAbBcCdDa123456";
console.log(str.substring(6,3));//cCd
console.log(str.substring(3,6));//cCd
</script>
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toString() 返回字符串对象值(显式强制性转化)
<script type="text/javascript">
var str=123;
/*console.log(typeof(str));//number
console.log(typeof(str.toString()));//string
console.log(typeof(String(str)));*///string
</script>
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toLowerCase() 把字符串转换为小写<br />
<script type="text/javascript">
var str="aAbBcCdDa123456";
//console.log(str.toLowerCase());//aabbccdda123456
</script>
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toUpperCase() 把字符串转换为大写
<script type="text/javascript">
var str="aAbBcCdDa123456";
//console.log(str.toUpperCase());//AABBCCDDA123456
</script>
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trim() 移除字符串首尾空白
<script type="text/javascript">
var str=" aAbB cCdDa123456 ";
/*console.log(str.length);//25
console.log(str);// aAbB cCdDa123456
console.log(str.trim().length);//18
console.log(str.trim());*///aAbB cCdDa123456
</script>