What are the new ECMAScript6 grammars
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First, the premise:
New grammar of ECMAScript6
ECMAScript version of the new syntax, not all browsers are compatible, some browsers are compatible with parts
II. New Grammar of ECMAScript
1. Variable definition
Version 5: var variable name: the scope of use of variables is not clear
For (var I = 0; I
< 10; i++) { console.log("in:"+i) } console.log("out:"+i); 6版本： let const:声明变量 let 变量名 用于声明局部变量 作用范围：从定义行开始到所在代码块结束 for (let i = 0; i < 10; i++) { console.log("in:"+i) } console.log("out:"+i); const修饰的值不可变（相当于java中的final） const修饰的对象地址不可以变，但是属性可以变，可以修改属性 const student={id:1,name:"王恒杰"} console.log(student); //const修饰的对象地址不可以变，但是属性可以变，可以修改属性 student.id=2; console.log(student) //增加属性age student.age=18; console.log(student) 2、箭头函数 使用场景：匿名函数作为函数的参数 语法：()=>{} is equivalent to function () {} simplifies function
Version 5: function function xx () {}
Version 6: arrow function
/ / Arrow function
Function test (func) {
Func (1)
}
/ / 5 version: function function xx () {}
Test (function (I) {
Alert (I)
})
/ / 6 version: arrow function () = > {function body}
Test ((I) = > {
Alert (I)
})
Note:
(1) when the function has only one parameter, () can be omitted. The parameter is multiple or no argument needs to be added with parentheses.
(2) there is only one line of code in the function body, and {} can also be omitted.
(3) the arrow function does not have its own this. If the this in the arrow function represents the current vue object, it does not represent the current function.
3. Template string--
When defining a variable, you can use the html tag to include it in the variable
/ / template string
Let html= "Click me"
+ "Click me"
+ "Click me"
+ "Click me"
Console.log (html)
/ / template string
Let html1=-- asked me.
Click me.
Click me.
Click me--
Console.log (html1)
4. Create an object
/ / define object
Let id=1
Let name= "Wang Hengjie"
Let age=18
/ / version 5 encapsulates objects
Let student= {id:id,name:name,age:age}
Console.log (student)
/ / version 6 encapsulates objects
Var student2= {id,name,age}
Console.log (student2)
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