prototype的解读之Array

整理部分prototype的Array相关的api

1、first()

原api的用途：

Returns the first item in the array,or undefined if the array is empty.

返回数组的第一项或者当数组为空时，返回undefined

用例：

["zhang","yao","chun"].first(); //"zhang"
[].first(); //undefined

["zhang","yao","chun"].first(); //"zhang"[].first(); //undefined

源码展示：

first : function(){
return this[0];
}

first : function(){ return this[0];}

2、last()

原api的用途：

Returns the last item in the array,or undefined if the array is empty.

返回数组的最后一项，或者当数组为空时，返回undefined

用例：

["zhang","yao","chun"].last(); //"chun"
[].last(); //undefined

["zhang","yao","chun"].last(); //"chun"[].last(); //undefined

源码展示：

last: function(){
return this[this.length - 1];
}

last: function(){ return this[this.length - 1];}

3、clone()

原api的用途：

Returns a duplicate of the array,leaving the original array intact.

返回原来数组的复制，原来那个数组没有任何变化。

用例：

["zhang","yao","chun"].clone(); //["zhang","yao","chun"]

["zhang","yao","chun"].clone(); //["zhang","yao","chun"]

源码展示：

clone:function(){
return [].concat(this);
}

clone:function(){ return [].concat(this);}