Js array method is summarized

1.some()方法

总结：
/* 1.some 方法不会改变原数组 2.someThe method loops through the elements of the compound condition and returnstrue,否则就返回false 3.someThe method does not iterate over an empty array machine **/
    let arr=[1,2,3,4,5,6,7,8];
    let hasItem1= arr.some(item=>{
    
    	return item>4
    })
    let hasItem2= arr.some(item=>{
    
    	return item>20
    })
    console.log(hasItem1,hasItem2)

2.every()方法

总结：
/** 1.everyThe method is executed for each item in the arraycallback函数,并且,All items are returned only if they meet the conditionstrue 否则,返回false 2.every也不会改变原数组 */
let arr=[1,2,3,4,5,6,7,8];
  let arr2 = arr.every(item=>{
    
      return item>4
   })
   let arr3 = arr.every(item=>{
    
      return item>10
   })

3.filter()方法

总结：
/** 1.filterIterates over each item in the array,And it will put the data of the compound condition into a new array and return it 2.没有符合条件的,则返回一个空数组 */
	let arr=[1,2,3,4,5,6,7,8];
    let arr4= arr.filter(item=>{
    
      return item>4
    })
    let arr5= arr.filter(item=>{
    
      return item>20
    })
    console.log(arr4)
    console.log(arr5)

4.map()方法

总结：
/** 1.mapIterates over each item in the array,并且返回一个新的数组 2.map不会检测空数组 */
	let arr=[1,2,3,4,5,6,7,8];
    let arr6=arr.map(item=>{
    
      return item+2
    })
    console.log(arr6)
    

5.reverse()方法

	let arr=[1,2,3,4,5,6,7,8];
 // reverse() 方法 The data inside the array is reversed Change the data in the original array
    let arr7= arr.reverse();
    //返回的结果便是 8,7,6,5,4,3,2,1

6.pop()方法

总结：
/** Removes and returns the last item of the array */
 let arr8= arr.pop();
  console.log(arr8)  
  console.log(arr) 

7.shift()方法

总结：
/** shift Removes and returns the first element of the array */
 let arr9= arr.shift();
  console.log(arr9)  
  console.log(arr) 

8.push()方法

总结：
/** 在数组后面pushEnter one or more items of data */
 let arr10= arr.push(12,17,18,19);
  console.log(arr10)  
  console.log(arr10) 

9.unshift()方法

总结：
/** Insert one or more items of data in front of the array */
  arr.unshift(11,14,15,16);
  console.log(arr)  

10.slice()方法

//Intercept some data of the array (开始下标,结束下标),Do not write closing subscripts,It means to truncate to the end at the beginning subscript position
let arr11=arr.slice(1,4)
//也可以用-1截取最后一项
 let arr12=arr.slice(-1);

//Some have said yes before 可以截取 （-1,4）intercept,我没有成功,It shows empty here,I hope someone who knows can give me some guidance.

11.sort()方法

总结：
/** 1.// sortSorting generally converts elements in an array into strings,比较字符串的Unicode 位点进行排序 2.Arrays can be sorted in ascending and descending order */
   let arr20= arr.sort((a,b)=>a-b); //升序
   console.log(arr20)
   let arr21= arr.sort((a,b)=>b-a);  //降序
    
    console.log(arr21)

12.concat()方法

let arr1=[4,5];
let arr=[1,2,3]
let arr2=arr.concat(arr1)
arr2的结果就是 1,2,3,4,5

The above is what we need nowjsArray of some commonly used methods.If there are errors, you can leave a message to discuss