“...args"是什么意思?(三个点)在函数定义中? [英] What is the meaning of "...args" (three dots) in a function definition?
问题描述
在 Javascript 中阅读这个语法真的让我感到困惑:
It was really confusing for me to read this syntax in Javascript:
router.route('/:id')
.put((...args) => controller.update(...args))
.get((...args) => controller.findById(...args));
...args 是什么意思?
推荐答案
对于 (...args) =>
,...args
是一个rest 参数.它始终必须是参数列表中的最后一个条目,并且将被分配一个数组,该数组包含尚未分配给先前参数的所有参数.
With respect to (...args) =>
, ...args
is a rest parameter. It always has to be the last entry in the parameter list and it will be assigned an array that contains all arguments that haven't been assigned to previous parameters.
它基本上替代了参数
对象.而不是写
It's basically the replacement for the arguments
object. Instead of writing
function max() {
var values = Array.prototype.slice.call(arguments, 0);
// ...
}
max(1,2,3);
你可以写
function max(...value) {
// ...
}
max(1,2,3);
此外,由于箭头函数没有 arguments
对象,这是创建可变参数(箭头)函数的唯一方法.
Also, since arrow functions don't have an arguments
object, this is the only way to create variadic (arrow) functions.
作为controller.update(...args)
,见foo"是什么意思(...arg)"(函数调用中的三个点)? .
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