八、字符串

一、增加、查询

1-1concat、indexOf

<script>
        /* 基本类型的方法都不可以改变它原来的值 */
        var str = "hello world"
        /* 增加 */
        str = str.concat("good")
        console.log(str)
        /*查询 indexOf -->可以查询字符串值的下标  */ 
        console.log(str.indexOf("g"))   
    </script>

1-2str-查询

 <script>
        /* slice 
        substring
        substr*/
        var str = "hello world";
        console.log(str.slice(0,3)) //startIndex<=num<end  
        console.log(str.substring(0,3))  
        console.log(str.substr(0,4))
    </script>

转数组

1-1拆分成数组 split

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

实例

1-1

 <script>
                var str = "let's go home";
                /* s'tel og emoh */
                /* 将字符串分割为数组 */
                var arr = str.split(" ");
                /*  ["let's", "go", "home"] */
               var newArr = arr.map(item=>{
                   return item.split("").reverse().join("")
               })
                /*  [[l,e,t,',s], [g,o], [h,o,m,e]] */
                /*  [[s,',t,e,l], [o,g], [e,m,o,h]] */
                /* ["s'tel","og","emoh"] */
                /* s'tel og emoh */
                console.log(newArr.join(" "))       
            </script>

1-2

<script>
        var str = "let's go home";
        /* s'tel og emoh */
        /* 将字符串分割为数组 */
        var arr = str.split(" ");
        /*  ["let's", "go", "home"] */
        var all=[];
        arr.forEach(item=>{
            let i = item.split("").reverse().join("")
            all.push(i)
        })
        /*  [[l,e,t,',s], [g,o], [h,o,m,e]] */
        /*  [[s,',t,e,l], [o,g], [e,m,o,h]] */
        /* ["s'tel","og","emoh"] */
        /* s'tel og emoh */
        console.log(all.join(" "))       
    </script>

1-3

<script>
        /*  */
        var obj = [{name:"晓星尘",age:10},{name:"宋岚",age:5},{name:"江厌离",age:6}]
        /* 1.["晓星尘","宋岚","江厌离"] */
        /* 2.晓星尘/宋岚/江厌离 */
        /* ollName = "晓星尘/宋岚/江厌离" */
        var newArr = obj.map(item=>{
            return item.name
        })
        console.log(newArr.join("/"))
    </script>

1-4search

<script>
        /* search 
        -1 字符串不包含这个值
        startsWith 是否包含某个值*/
        var str = 'hello world';
        var http = "https://ww.baidu.com"
        console.log(str.search("i"))
        console.log(http.startsWith("https")) 
</script>

1-5

<script>
        var cities = [{spell:"tianmen",city:"天门"},{spell:"tianjing",city:"天津"},
        {spell:"tianshui",city:"天水"},{spell:"wuhan",city:"武汉"}] 
        /* 天或tian 开头的  将city添加到一个数组中 */
        /* var allCities = [] */
        var allCities = [];
        cities.forEach(item=>{
            if(item.spell.startsWith("tian") || item.city.startsWith("天")){
                allCities.push(item.city)
            }
        })
        console.log(allCities)
    </script>

1-6match

<script>
        /* match
        -->返回匹配的值，是一个数组 
        replace()*/    
        var str = "hello";
        console.log(str.match("e"))
        console.log(str.replace("1","g"))
    </script>