JavaScript the Good Parts: unshift function -

JavaScript the Good Parts: unshift function -

i'm reading javascript:the parts crockford , i'm having problem understanding reimplementation of unshift method in book.here the code:

array.method('unshift', function ( ) { this.splice.apply(this, [0, 0].concat(array.prototype.slice.apply(arguments))); homecoming this.length; });

it useful if go through happening step step. 1 of things don't understand why concatenates [0 , 0] result of array.prototype.slice.

why concatenates [0 , 0] result of array.prototype.slice

the first 2 arguments of splice (which resulting array applied to) are:

index 0 because adding front end of array howmany (to remove) 0 because adding new elements

the remaining arguments values added front end of array, taken array.prototype.slice.apply(arguments) (to convert info arguments object info in array).

javascript