数组的方法

1、改变原数组
push、pop、shift、unshift、sort、reverse、splice
2、不可改变原数组
concat、join、split、toString、slice

var obj = {
}
obj.fun = function(){
  console.log(1)
}
//这个是函数表达式

splice(从第几位开始，截取多少的长度，在切口处添加新数据)

var arr = [1,2,3,4,5,6]
arr.splice(1,4,0,0,0,0,0)
console.log(arr)    //[1, 0, 0, 0, 0, 6]

var arr = [1,2,3,4,5,6]
arr.splice(1,0,0,0,0,0)
console.log(arr)    //[1, 0, 0, 0, 0, 2, 3, 4, 5, 6]  第二个参数为0不切数组，在切口处插入

sort() 排序

//升序
var arr = [4,5,6,4,3,4,5,6,7,9,9]
arr.sort()
console.log(arr)    //[3, 4, 4, 4, 5, 5, 6, 6, 7, 9, 9]
//降序
var arr = [4,5,6,4,3,4,5,6,7,9,9]
arr.sort().reverse()
console.log(arr)    //[9, 9, 7, 6, 6, 5, 5, 4, 4, 4, 3]

var arr = [4,5,6,4,3,4,5,6,7,9,9]
// 1、必须写两形参
// 2、为正数，那么后面的数在前
// 3、为0，不动
arr.sort((a,b)=>{
    return a - b    //升序 b - a降序
})
console.log(arr)    //[3, 4, 4, 4, 5, 5, 6, 6, 7, 9, 9]

//产生随机数
var arr = [4,5,6,4,3,4,5,6,7,9,9]
// 1、必须写两形参
// 2、为正数，那么后面的数在前
// 3、为0，不动
arr.sort(()=>{
    return Math.random()-0.5
})
console.log(arr)    //每次结果不确定

//对象排序
var obj1 = {
        age:12
}
var obj2 = {
        age:14
}
var obj3 = {
        age:10
}
var arr = [obj1,obj2,obj3];
    arr.sort((a,b)=>{
        return a.age - b.age
})
console.log(arr)    //升序

//按照字符串长度排序
var arr = ['sdfs','sdfsfdfdsfdsfds','sdf','dfgdfg']
arr.sort((a,b)=>{
    return b.length - a.length
})
console.log(arr)    //["sdfsfdfdsfdsfds", "dfgdfg", "sdfs", "sdf"]

join()

var arr = [1,2,3,4,5]
console.log(arr.join(' '))    //1-2-3-4-5

split()

var arr = [1,2,3,4,5];
var str = arr.join('-');
console.log(str)    //1-2-3-4-5
console.log(str.split('-'))    //["1", "2", "3", "4", "5"]

数组去重

var arr = [1,1,1,1,5,5,5,4,5,6,7,8,9,2]

Array.prototype.unique = function(){
            var temp = [],
            arr = [],
            len = this.length;

            for(var i = 0; i < len; i ++){
                if(!temp[this[i]]){
                    temp[this[i]] = 'a';
                    arr.push(this[i])
                }
            }
            return arr;
        }
//[1, 5, 4, 6, 7, 8, 9, 2]

3、some()方法

var arr = [1,2,3,4,5];
 var arr1 = arr.some((item,index,arr)=>{
       console.log(item,index,arr)
       return item >=5
})
console.log(arr1)    //true