The array methods often encountered in js learning are summarized well.

Summary of js array method: 1. Insert push at the end of the queue, 2. Delete the last item deleted at the end of the queue and return pop, 3. Insert unshift() at the head of the team, 4. Delete shift() at the head of the team, 5. Array one adds array two concat()

1. Insert push

   var colors = ["red","green"];
   colors.push("black"):
   console.log(colors); //["red","green","black"]

2 at the end of the queue and delete the last item deleted and return pop

   var colors = ["red","green","black"];
   var item = colors.pop();
   console.log(item); //"black"

3. Queue First insert unshift()

   var colors = ["red","green"];
   colors.unshift("black");
   var item = colors.pop();
   console.log(item); //"black"

4. First delete shift()

   var colors = ["red","green","black"];
   colors.shift();
   console.log(colors); //["green","black"]

5. Add array one to array two concat()

   var colors = ["red","green","black"];
   var colors2 = colors.concat("yellow",["blue","brown"]);
   console.log(colors); //["red","green","black"]
   console.log(colors2); //["red","green","black","yellow","blue","brown"]

6. Array interception slice ()
Pass only one parameter: intercept from the subscript of the parameter in the array to the end of the array.

   var colors = ["red","green","black"];
   colors.slice(1); //["green","black"]
   console.log(colors); //["red","green","black"]

Pass two parameters: the first is the starting position of interception, the second is the end position of interception

   var colors = ["red","green","black","yellow","blue","brown"];
   colors.slice(1,3)//从位置1开始，到位置2结束["green","black"];

7, splice() method of array

   有三种用法：

• Delete: You can delete any number of items by specifying two parameters: the first parameter is the starting position of deletion, and the second parameter is the number of deleted items.

• Insert: You can insert any number of items into the specified position by providing 3 parameters: starting position, 0 (the number of items to be deleted) and the items to be inserted. For example: splice(2,0,"red","green") will insert the strings "red" and "green" starting from position 2 of the current array.

• Replacement: You can insert any number of items into the specified position and delete any number of items at the same time. You only need to provide 3 parameters: the starting position, the number of items to be deleted, and the number of items to be deleted. Any number of items inserted. The number of items inserted does not necessarily equal the number of items deleted. For example: splice (2,1,"red","green") will delete the item at position 2 of the current array, and then insert the string starting from position 2.

   var colors = ["red","green","black"];
   var removed = colors.splice(0,1);
   console.log(colors); //["green","black"]
   console.log(removed); //["red"]
    
   removed = colors.splice(1,0,"yellow","orange");
   console.log(colors); //["green","yellow","orange","black"]
   console.log(removed); //[]

   removed = colors.splice(1,1,"red","purple");
   console.log(colors); //["green","red","purple","orange","black"]
   console.log(removed); //["yellow"]

8. Position methods indexOf() and lastIndexOf()

Related articles:

Summary of js array operation methods (must read Article)

Summary of JS array deduplication method

Related videos:

js arrays and objects-Qianfeng Education JS Practical video tutorial

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