concat

<script>
        var str = "hello";
        var s = "world";
        console.log(str.concat(" ").concat(s));//hello world
</script>

字符串模板

作用:可以在字符串中使用变量

<script>
        var str  = 10;
        var b = "hello";
        console.log(str+b);
        var sum = `${str}hello`;
        console.log(sum)
    </script>

slice(startIndex,endIndex)

<script>
        var str  ="hello";
        console.log(str[0]);//h
        console.log(str.slice(0,3))//hel
</script>

substr(index,length) \substring(startIndex,endIndex)

<script>
        var str = "hello";
        console.log(str.substr(2,3));//llo
        console.log(str.substring(0,2))//he
    </script>

length 字符串的长度

<script>
        var str = "hello";
        console.log(str.length)//5
        var s = "故事的结尾，心上人";
        console.log(handleStr(s))//故事的结尾...
        function handleStr(value) {
            if (value.length > 5) {
                return value.slice(0, 5) + "..."
            }
            return value;
        }
</script>

charAt

输出某一位下标值的字符

<script>
        var str = "hello";
        console.log(str.charAt(1))//e
</script>

indexof

输出某一字符的下标值

<script>
        var str ="hello";
        console.log(str.indexOf("h"))//0
        console.log(str.indexOf("h"))//-1
</script>

search

<script>
        /* search 返回值的下标,没有返回-1,和indexOf类似 */
        var str = "你是谁";
        var index = str.search("你");
        console.log(index)
        console.log(str.indexOf("他"))
</script>

match

<script>
        /* match返回匹配的字符,返回一个数组 */
        var str = "helllllo";
        var arr = str.match("l");
        var arr1 = str.match("a");
        console.log(arr[0]);//l
        console.log(arr1);//null
</script>

includes

字符串是否包含某位(多位)字符

<script>
        var str ="hello";
        console.log(str.includes("he"))//true
</script>

replace

<script>
        /* replace可以替换字符 */
        var str = "hello";
        console.log(str.replace("l","*"))
</script>

split

<script>
        /* split(seprate) */
        var str  ="hello";
        var arr = str.split("");
        console.log(str.split())//["hello"]
        console.log(arr);//["h", "e", "l", "l", "o"]
        console.log(str.split("e"))//["h", "llo"]
</script>

例子(将hello反转为olleh)

<script>
        var str = "hello"
        var arr = str.split("");
        arr.reverse();
        var s = arr.join("")
        console.log(s);
</script>

trim

<script>
        httpList()
        var a = "  hello world   "
        var b = a.trim()
        console.log(a.length)//  hello world   /
        console.log(b.length)//hello world
        console.log(a.length)//16
        console.log(b.length)//11
    </script>

字符串转成正则表达式

var str = "/\\" + left[i] + "/";
var reg = eval(str)