js之作用域、evenLoop

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作用域
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var a = [1]
function fn () {
  a[1] = 1000
  a = [10]
  console.log('fn:', a)
}
fn()
console.log('window:', a)
// 'fn:'[10] => 'window:'[10]

var a = [1]
function fn (a) {
  a[1] = 1000
  a = [10]
  console.log('fn:', a)
}
fn(a)
console.log('window:', a)
// 'fn:'[10] => 'window:'[1, 1000]
EvenLoop
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setTimeout(() => {
  console.log('1')
})
var p = new Promise((res, rej) => {
  console.log('2')
  setTimeout(() => {
    console.log(3)
  })
  res()
})
p.then(() => {
  console.log(4)
}).then(() => {
  console.log(7)
})
setTimeout(() => {
  console.log(5)
})
console.log(6)
// 2 => 6 => 4 => 7 => 1 => 3 => 5