Table of contents
1. Two ways to create an array
1. The instanceof operator, which can be used to detect whether it is an array
3. Add and delete array elements
1. push() adds one or more array elements at the end of the array
3. pop() deletes the last element of the array and returns the value of the deleted element
4. shift() deletes the first element of the array and returns the value of the first element
Five, the case - array deduplication
1. Two ways to create an array
1. Using array literals
//创建数组
// 1.数组字面量
var arr = [1,2,3]
console.log(arr[0])
2. Use new Array()
//2. 利用new Array()
var arr1 = new Array(2);//这个2表示数组长度为2，里面是两个空数组元素
var arr2 = new Array(1,2,3)
console.log(arr1);
console.log(arr2);
2. Check if it is an array
1. The instanceof operator, which can be used to detect whether it is an array
var arr = [];
var obj = {}
console.log(arr instanceof Array)//true
console.log(obj instanceof Array)//False2. Array.isArray(parameter)
//2.Array.isArray H5新增的方法,ie9以上支持
console.log(Array.isArray(arr))//true
console.log(Array.isArray(obj))//False3. Add and delete array elements
1. push() adds one or more array elements at the end of the array
After the push is completed, the length of the new array is returned, and the original array will also change
//添加删除数组元素
var arr3 = [1,2,3];
// arr.push(4,'新增')
console.log(arr3.push(4,'新增'))
console.log(arr3)
2. arr.unshift() adds one or more array elements at the beginning of the array, and returns the length of the new array
//arr3.unshift('前面','新增')
console.log(arr3)
console.log(arr3.unshift('前面','新增'))
console.log(arr3)
3. pop() deletes the last element of the array and returns the value of the deleted element
4. shift() deletes the first element of the array and returns the value of the first element
//删除元素
console.log(arr3.pop())
console.log(arr3)
console.log(arr3.shift())
console.log(arr3)
4. Array index
indexOf(array element)
Returns the first index number that satisfies the condition, and searches from the front. If it cannot find an element in the array, it returns -1
lastIndexOf (array element), start searching from the back
Five, the case - array deduplication
//数组去重,封装一个去重的函数unique
function unique(arr){
var newArr = [];
for (var i= 0;i<arr.length;i++){
if(newArr.indexOf(arr[i])===-1){
newArr.push(arr[i]);
}
}
return newArr;
}
var demo = unique(['a','d','d','o','a','c'])
console.log(demo)
6. Convert array to string
1. toString() converts an array into a string
2. join('separator')
//数组转换成字符串
var arr4 = ['ggg','rrr','ppp'];
console.log(arr4);
console.log(arr4.toString());
console.log(arr4.join());
console.log(arr4.join('-'));
console.log(arr4.join('$'));
7. Others
concat(): connects two or more arrays without affecting the original array
returns a new array
slice(): Array interception slice(begin, end), returns a new array of intercepted items
splice(): Array deletes splice (the first number, the number of deletions), and returns a new array of deleted items, which will affect the original array