Why is the value of this tag 1 and this tag 2 different when the second callback is made by the two calls
?

 function a (val, callback) {
      callback.call(a,val,callback)
    }
    a(1,function b (val ,callback) {
        console.log(this, "1")
        console.log(val)
        console.log(callback)
        callback(2,function c(val, callback){
        console.log(this)
        console.log(val)
        console.log(callback)
        console.log("over")
      })
    })
    console.log("------------")
    a(1,function b () {
        console.log(this, "2")
        console.log(arguments[0])
        console.log(arguments[1])
        arguments[1](2,function c(){
        console.log(this)
        console.log(arguments[0])
        console.log(arguments[1])
        console.log("over")
      })
    })