js 改字母大小写

js字母大写:

<script>
    let b = 'abc'
    console.log(b.toLocaleUpperCase());   //ABC
    console.log(b.toUpperCase());          //ABC
    console.log(b.toLocaleLowerCase());     //abc
    console.log(b.toLowerCase());           //abc
</script>

　截取：

var heroes=["李白",'蔡文姬','韩信','赵云','甄姬','阿珂','貂蝉','妲己'];
console.log(heroes.slice(1))// [ "蔡文姬", "韩信", "赵云", "甄姬", "阿珂", "貂蝉", "妲己" ]
console.log(heroes.slice(1,-4))//  [ "蔡文姬", "韩信", "赵云" ] 开始索引1  结束索引8+(-4)=4
console.log(heroes.slice(1,-10)) //[ ] 开始索引1  结束索引8+(-10)=-2

改变this的指向：

    <script>
        let obj = {name:"张三"}

        function fn(name){
            console.log(this,name);
        }
        // fn.call(obj,"文种玉");    //后面携带的参数是""双引号
        // fn.apply(obj,["文渊"])     //后面携带的参数是数组括号
        fn.bind(obj,"文天祥")() //他不会调用,传参与call一样    //后面携带的参数和.call一样
    </script>