扩展运算符... rest运算符
<script>
let arr = ['apple','banana','orange'];
console.log(arr);
console.log(...arr);
</script>
let arr = ['apple','banana','orange'];
console.log(arr);
console.log(...arr);
</script>
... :
[1,2,3,4] -> ... [1,2,3,4] -> 1,2,3,4,5
...:
1,2,3,4,5 -> ...1,2,3,4,5 -> [1,2,3,4,5]
[1,2,3,4] -> ... [1,2,3,4] -> 1,2,3,4,5
...:
1,2,3,4,5 -> ...1,2,3,4,5 -> [1,2,3,4,5]
剩余参数必须放在最后面
function show(a,b,...c){
console.log(a,b);
console.log(c);
}
show(1,2,3,4,5)
console.log(a,b);
console.log(c);
}
show(1,2,3,4,5)
箭头函数 =>
() =>{ 语句 return}
//等同于
var f = function(v){
return v;
}
var sum = (num1,num2) => num1 + num2;
//等同于
var sum = function(num1,num2){
return num1 + num2;
}
[1,2,3].map(function (x) {
return x * x;
});
//箭头函数写法
[1,2,3].map(x => x *x); //简洁了许多
注意:
this
问题,,不在是运行时所在的对象
- 箭头函数里面没有
arguments
, 用 ‘...
’ - 箭头函数不能当构造函数