ES6笔记③

1.查找关键字  includes(); 返回布尔值

//①：includes -->代替-->indexof-->返回布尔值
    var str = "769909303";
    console.log(str.indexOf("9"));//2
    console.log(str.includes("9"));//true

2. 重复字符 repeat();

//②：repeat -->重复
    console.log('meow'.repeat(3));

3.模块字符串 3个特性： ①：特殊字符再也不用转义了。 ②：变量拼接 + 换行拼接 ③：支持表达式

//3. 模板字符串 --> 对字符串中的特殊字符，再也不用转义了
            var text = "This string contains "double quotes" which are escaped.";
                console.log(text);            
            var text2 =    `This string contains "double quotes" which are escaped.`;    
                console.log(text2);

//拼接变量语法: ``+${};  
const name = 'Tiger';
const age = 13;
console.log(`My cat is named ${name} and is ${age} years old.`);
//换行拼接
let text = ( `cat
　　dog
　　nickelodeon`
　);

//支持表达式
let today = new Date();
let text = `The time and date is ${today.toLocaleString()}`;

4.结构--> 更方便拿到数组、对象中的值。注意：等号两边都不限制个数，像创建变量一样，默认为undefined。对象解构时，变量名要同对象名

//不限制个数
var arr = [0,1,2,3,4,5,6,7,8,9];
var  [a,b,c,d] = [arr[0],1,2,3,4];
    console.log(a);

var obj = {a:10,b:20};
var {a,b,c} = obj;
      console.log(a);

/*[创建一个关联变量数组或变量对象，挨个赋值嘛]*/

5.创建函数时，初始化默认值 ES6写法

function fun(x=0,y=0){
    return x+y;
}
console.log(fun(5));//5
console.log(fun(5,10));//15

6.更简洁的合并数组  ...自定义剩余参数

var arrreat  = [5,6];
var news = [1,2,3,4,...arrreat,7];
console.log(news);//1234567