ECMAScript 6知识点总结 --- 函数

• 函数默认参数

  let func = (x = 1, y = 2) => {
      console.log(x ,y)
  }
  func()
  // 1, 2
  
  let func2 = ({x=0, y=0}={}) => {
      console.log(x, y)
  }
  func2()
  // 0, 0
  func2({x:1, y:2})
  // 1, 2

• 函数默认参数已经定义了，不能再次声明

  let func = (x=1, y=2) => {
      let x = 2  // 错误
      console.log(x ,y)
  }
  func()
  // Uncaught SyntaxError: Identifier 'x' has already been declared
  

• 与...结合使用

  let func = (...a) => {
      console.log(a)
  }
  func(1,2,3,4,5)
  // [1,2,3,4,5]
  
  
  let func = (a,b,c) => {
      console.log(a,b,c)
  }
  func(...[1,2,3])
  // 1,2,3
  
  
  // 剩余运算符 必须在最后一个参数
  let func = (a,b,...c) => {
      console.log(a,b,c)
  }
  func(1,2,3,4,5)
  // 1,2,[3,4,5]