JavaScript: this apply call

 

let arr = Array.from('vaunt')
console.log(arr.slice(1, 3))

let slice = Array.prototype.slice
console.log(slice)  // [Function: slice]
let bounded = slice.bind(arr)
console.log(bounded)  // [Function: bound slice]

let b1 = slice.call(arr, 1, 3)  // call内部的this指向slice函数, slice变成bounded, slice内部this指向arr( 等价于arr.slice() )
console.log('b1:', b1)

let b2 = slice.apply(arr, [1, 3])  // apply内部的this指向slice函数, slice变成bounded, slice内部this指向arr( 等价于arr.slice() )
console.log('b2:', b2)

// call内部的this指向apply函数, apply变成bounded, apply内部this指向slice( 等价于slice.apply() )
let b3 = Function.prototype.apply.call(slice, arr, [1, 3])
console.log('b3:', b3)

let b4 = Function.prototype.apply.apply(slice, [arr, [1, 3]])
console.log('b4:', b4)

let b5 = Function.prototype.call.apply(slice, [arr, 1, 3])
console.log('b5:', b5)

let b6 = Function.prototype.call.call(slice, arr, 1, 3)
console.log('b6:', b6)