函数扩展
// 函数默认值
const test = (x, y = 'world') => {
console.log(x, y)
}
// hello world
test('hello')
// hello ronle
test('hello', 'ronle')
// 作用域
let x = 'demo'
const test = (x, y = x) => {
console.log(x, y)
}
// demo demo
test(x)
// hello hello
test('hello')
// 不确定参数个数
const test = (...arg) => {
for (let v of arg) {
console.log(v)
}
}
test(1, 2, 3, 4, 'a')
const test = (x, ...arg) => {
console.log(x)
for (let v of arg) {
console.log(v)
}
}
test(1, 2, 3, 4, 'a')
展开运算符
// 1 2 3 4 5 6 7
console.log(...[1, 2, 3, 4, 5, 6, 7])
// a 1 2 3 4 5 6 7
console.log('a', ...[1, 2, 3, 4, 5, 6, 7])
箭头函数
const arr = v => v * 2
const arr2 = () => 10
// 6
console.log(arr(3))
// 10
console.log(arr2())
// 尾调用(某个函数的最后一步是调用另一个函数)
const run = (x) => console.log(x)
const person = (x) => {
return run(x)
}
person(123)
