1 Creation of arrays
var arr1 = new Array(); var arr2=[1,2,3];
2 Commonly used methods for arrays:
push, pop, shift, unshift, splice, slice, sort, reverse
2.1 push method: insert elements at the end of the element
var arr=[1,2,3]; var result = arr.push(1,3,4);//返回新数组的长度 console.log("arr:"+arr); console.log("result:"+result);
Result:
arr:1,2,3,1,3,4
result:6
2.2 pop method: Pop an element at the end of the element
var arr=[1,2,3]; var result = arr.pop();//返回弹出元素的值 console.log("arr:"+arr); console.log("result:"+result);
Result:
arr:1,2
result:3
2.3 shift method: pop up an element at the beginning of the element
var arr=[1,2,3]; var result = arr.shift();//返回弹出元素的值 console.log("arr:"+arr); console.log("result:"+result);
result:
arr:2,3
result:1
2.4 unshift method: insert an element at the beginning of the element
var arr=[1,2,3]; var result = arr.unshift(4,5);//返回新数组的长度 console.log("arr:"+arr); console.log("result:"+result);
result:
arr :4,5,1,2,3
result:5
2.5 splice method: intercept the array, then insert the data, directly operate the array itself
var arr=[1,2,3,4,5]; arr.splice(1,2,3,4); console.log("arr:"+arr);
Result:
arr:1,3,4,4 ,5
Analysis:
The first parameter: the starting position of interception
The second parameter: the number of interceptions
After the second parameter: the inserted data, if there is no third parameter, it will not be inserted
2.6 slice method: Intercept the array, but do not operate on the array itself
var arr=[1,2,3,4,5]; var result =arr.slice(2,4); console.log("arr:"+arr); console.log("result:"+result);
Result:
arr:1,2,3,4,5
result:3,4
Analysis:
First one Parameter: The starting position of interception is a closed interval
The second parameter: The end position of interception is an open interval
Such as: [2,4)
2.7 concat method: Splice arrays, but do not operate on the array itself
var arr1 =[1,2,3]; var arr2=[3,4,5]; var result = arr1.concat(arr2); console.log("arr1:"+arr1); console.log("arr2:"+arr2); console.log("result:"+result);
Result:
arr1:1,2,3
arr2:3,4,5
result:1,2,3,3,4,5
2.8 join method: For each element of the array Insert elements in between, but do not operate the array itself
var arr =[1,2,3]; var result =arr.join("-"); console.log("arr:"+arr); console.log("result:"+result);
Result:
arr:1,2,3
result:1-2-3
2.9 reverse method: Reverse the position of the elements in the array
var arr =[1,2,3]; var result =arr.reverse(); console.log("arr:"+arr);
Result :
arr:3,2,1
2.10 sort method: Sort the elements in the array (defective)
var arr =[4,10,1,5]; var result =arr.sort(); console.log("arr:"+arr);
Result:
arr:1,10,4,5
Analysis:
In During the comparison process, this 10 is compared according to the first digit and then the second digit, so it is ranked behind 1 and in front of 4.
2.11 sort method expansion
var arr =[4,10,1,5]; function compare(value1,value2){//自定义排序规则 if(value1>value2){ return 1; }else if(value1<value2){ return -1; }else{ return 0; } } var result =arr.sort(compare);使用自定义的排序规则 实现从小到大排序 要想实现从大到小 修改排序规则 console.log("arr:"+arr);
Result:
arr:1,4,5,10