1. Array operations
Array operations: change of cells in the array, adding cells, deleting cells, modifying cells.
1. [Add] of the array
example:
let obj = [‘张三’，‘李四’，‘王五’]；
Specifically, there are two ways to achieve this:
1.1 push（）
【结尾处】Adding a new element to an array
Syntax format: array name.push (new unit)
obj.push('赵四');
console.log(obj);// [‘张三’，‘李四’，‘王五’,'赵四']
1.2 unshift（）
【开始】add a new element to the array
Syntax format: array name.unshift (new unit)
obj.unshift('哈哈')
console.log(obj);// ['哈哈'，‘张三’，‘李四’，‘王五’,'赵四']
1.3 Supplement:
New units can also be added by index value
ArrayName[IndexValue] = NewCell
But it should be noted that the index does not exist in the original array, if it exists, the array unit is modified.
2. [Delete] of the array
example:
let arr = [‘张三’，‘李四’，‘王五’]；
Specifically, there are two ways to achieve this:
1.1 pop（）
The array can be 【最后一个单元】deleted, and the deleted unit can be obtained.
Syntax format: array name.pop()
let aa = arr.pop（）;
console.log（aa）; // 王五
1.2 shift（）
The cells of the array can 【第一个】be deleted, and the deleted cells can be obtained.
Syntax format: array name.shift()
let bb = arr.shift（）;
console.log（bb）; // 张三
Summarize:
After passing
popandshiftdeleting the unit, the deleted unit can be obtained.
For example:
let heroes = ['Zhang Fei', 'Zhang Fei 1', 'Zhang Fei 2'];
let aa = heroes.pop(); // 'Zhang Fei 2'
3. Universal modification method splice
When operating on array units, you can use splice to operate on units at [any] position.
It can be added, deleted, or even modified!
Grammar format: array name.splice (subscript, number)
let arr = [‘张三’，‘李四’，‘王五’]；
1.1 删除
Grammar format: array name.splice (subscript, number)
arr.splice(1,1);
console.log(arr);// [‘张三’，‘王五’]
For example:
let heroes = ['Zhang Fei', 'Zhang Fei1', 'Zhang Fei2'];
heroes.splice(1,1); // 'Zhang Fei1' is deleted from the array
1.2 Modifications
Grammar format: array name.splice (subscript, number, new unit)
There are as many new units as there are.
// 修改一个
// 数组名.splice（下标，个数，新单元）
arr.splice(0,1,'小张三')
console.log(arr);// ['小张三'，‘李四’，‘王五’]
// 修改二个
// 数组名.splice（下标，个数，新单元，新单元）
arr.splice(0,2,'小张三','小李四')
console.log(arr);// ['小张三'，'小李四'，‘王五’]
1.3 add
Syntax format: array name.splice(subscript, 0, new unit)
arr.spilce(0,0,'测试')
console.log(arr);// ['测试'，‘张三’，‘李四’，‘王五’]