A question about JavaScript's slice and splice methods

Question

I came across the following code:

var f = function () {
    var args = Array.prototype.slice.call(arguments).splice(1);

    // some more code 
};
         


        

Answer 1

The returned value of a splice is an array of the elements that were removed, but the original array (or array-like object), is truncated at the splice index.

Making a copy with slice preserves the original arguments array, presumably for use later in the function.

In this case the same result can be had with args = [].slice.call(arguments, 1)

function handleArguments(){
 var A= [].slice.call(arguments).splice(1);
 //arguments is unchanged
 var s= 'A='+A+'\narguments.length='+arguments.length;

 var B= [].splice.call(arguments, 1);
 // arguments now contains only the first parameter
 s+= '\n\nB='+B+'\narguments.length='+arguments.length;
 return s;
}

// test
alert(handleArguments(1, 2, 3, 4));

returned value:
//var A= [].slice.call(arguments).splice(1);
A=2,3,4
arguments.length=4

//var B= [].splice.call(arguments, 1);
B=2,3,4
arguments.length=1