数组
创建
let arry1=new Array();
let arry2=new Array(10);
let Array3=new Array("fff","fbbb","mooo");
let array4=["bv","mn","op"];
let array5=[0,2,9,10,20,8];
常见方法 push shift join toString pop unshift sort concat slice splice indexOf every some filter
let arry5=[0,1,2,3];
let atty6=arry5.push(8,9,10)//将数组添加到末尾
console.log(arry5);
let item=arry5.shift();//移除第一项并返回该项
console.log(item);
if(Array.isArray(arry1)){};//判断是否为数组
console.log(Array3.join('_'));//设置连接符
console.log(Array3.toString());//数组转字符串
console.log(Array3.pop());//移除数组末尾最后一项并返该项
console.log(Array3.unshift("000","sdbasb"))//在数组的前端添加任一一项并返回数组长度
console.log(Array3);
console.log(Array3.sort());//首先将数组里面的值转成字符串。然后比较字符串的编码的大小
function compare(values1,values2)
{
return values1-values2;
}
array5.sort(compare);//按照函数比较结果排序
console.log(array5);
//concat
console.log(Array3.concat(array4));
///slice
console.log(array5.slice(1));
console.log(array5.slice(1,3));
// console.log(array5.slice(-1,-3));//负数加上数组长度,等同于array5.slice(5,3)
//splice 获取到截取是我内容 将截取内容从原数组删除
let arraysplice=["00","11","22","330","44"];
console.log(arraysplice.splice(0,2));//截取从0到2的项并移除
console.log(arraysplice);
//插入
let remove= arraysplice.splice(0,1,"dfd","gfnfdn")
console.log(remove);
console.log(arraysplice);
//代替
let remove0= arraysplice.splice(1,1,"...","```")
console.log(arraysplice);
//indexof(item)从头往后查找该项索引
let array5indexof=[0,2,3,9,10,20,8];
console.log(array5indexof.indexOf(3));//从0开始查找3
console.log(array5indexof.indexOf(3,2));//从2开始查找3
console.log(array5indexof.lastIndexOf(3));//从末尾开始查找3
console.log(array5indexof.lastIndexOf(3,2));//从2开始查找3
// every some filter
let array5i =[0,2,3,9,10,20,8];
let res1=array5i.every(function(item,index)
{
return item>8;
})
console.log(res1);
let res2=array5i.some(function(item,index)
{
return item>8;
})
console.log(res2);
//过滤
let res3=array5i.filter(function(item,index)
{
return item>8;
})
console.log(res3);
循环
for in 、for of、forEach、reduce
<script>
let obj={
name:"jimgreem",
age:55,
};
for(let key in obj)
{
console.log(key);
}
for(let key of Object.keys(obj))
{
console.log(key);
}
let arr=["red","ggg","blue"];
for (let item of arr)
{
console.log(item);
}
let arry=[3,20,51,23,10,88,3];
for (let i=0;i<arry.length;i++)
{
console.log(i);
}
arr.forEach(element => {
console.log(element);
});
var sum=arry.reduce(function(pre,cur){
return pre+cur;
},0);
console.log(sum);
var max=arry.reduce(function(pre,cur){
return Math.max(pre,cur);
});
console.log(max);
</script>