js

JS–数组中的方法

var a=[1,2,3];
Array.prototype.unshift=function () {
var str=””;var ary=null;
for(var i=0;i<arguments.length;i++){
str+=arguments[i]+”,”;
}
ary=eval(“[“+str+this+”]”);
for(var k=0;k<ary.length;k++){
this[k]=ary[k]
}
return ary.length;
};
console.log(a.unshift(20, 3));
console.log(a);

Array.prototype.push=function () {
for(var i=0;i<arguments.length;i++){
this[this.length]=arguments[i];
}
return this.length;
}
console.log(a.push(8, 9));
console.log(a);

Array.prototype.pop=function () {
var num=this[this.length-1];
this.length–;
return num;
}
console.log(a.pop());
console.log(a);

Array.prototype.shift=function () {
var num=this[0];
for(var i=1;i<this.length;i++){
this[i-1]=this[i];
}
this.length–;
return num
}
console.log(a.shift());
console.log(a);