JavaScript analog combination and concat

Definition and usage

The concat() method is used to concatenate two or more arrays.

This method does not change the existing array, but only returns a copy of the connected array.

grammar

(arrayX,arrayX,......,arrayX)

Returns a new array. This array is generated by adding all arrayX parameters to the arrayObject. If the parameter to perform the concat() operation is an array, then the elements in the array are added, not the array
。

We have two arrays like this

var arr1 = [1,2,3];
var arr2 = [4,5,6];

Task: Merge it like this, please provide at least two ideas.

var arr1 = [1,2,3,4,5,6];

Idea 1:We can add the values ​​in the second array one by one to the end of the first array.

1: How to add content to arrays? [] || push || shift

2: How to add value to the last index of the array? push || [array.length]

3: How to add content to the array one by one? for

4: How many times does the for loop occur? You can cycle as many times as you want, that is, the length of arr2

5: What to add? How to get the value in arr2, arr[?]

Code implementation:

var arr1 = [1,2,3];
var arr2 = [4,5,6];
for(var i=0;i<;i++){
(arr2[i]);
}
(arr1); //[1, 2, 3, 4, 5, 6]

The problem is that the concat method provided by native js will not modify the content of the original array (arr1), but will return a new array.

Analysis: Since we want to return a value, we can define a function and then define a variable to receive the good value we added, but we will have a problem, that is, we cannot push the content on arr1, otherwise the content of the original array will still be modified. So I think I want to copy the original array, but there is another problem, that is, the object is a reference type. Simply put, although we can copy array 1 into a variable, if I modify the value in it in the form of push or [], or add it, then our original array will also be modified (if you don't know what the reference type is, you can go to the first page or the second page of my blog) This is not the result we want, but we must copy arr1. What solution do you have at this time?

Solve array reference issues:

for(var i=0;i<;i++){
arr3[i] = arr1[i];
}

My idea is to add the values ​​of array 1 to the arr3 array one by one. At this time, arr3 is like this

(arr3) //[1, 2, 3]

Task: Add the so value of arr2 in this new array arr3. The method is the same as the first step. If you forget to look back.

Code implementation:

var arr1 = [1,2,3];
var arr2 = [4,5,6];
var arr3 = [];
for(var i=0;i<;i++){
arr3[i] = arr1[i];
}
for(var i=0;i<;i++){
(arr2[i]);
}
(arr3);

Question: Although this has implemented the merge of arrays, I have to rewrite a copy every time I merge, which is too troublesome, so we have to find a way to encapsulate it into a function, and call it next time we want to use it.

var arr1 = [1,2,3];
var arr2 = [4,5,6,7];
function Concat(arr1,arr2){
var arr3 = [];
for(var i=0;i<;i++){
arr3[i] = arr1[i];
}
for(var i=0;i<;i++){
(arr2[i]);
}
return arr3;
}
(Concat(arr1,arr2));

Idea 2:

Analysis: Convert both arr1 and arr2 into strings, then add these two strings to a combination, and then convert the string into an array.

Code implementation:

var arr1 = [1,2,3];
var arr2 = [4,5,6,7,8,9];
var arr3 = ((",")+","+(",")).split(",");

Something went wrong, the value in this array is a string.

["1", "2", "3", "4", "5", "6", "7", "8", "9"]

Solution: traverse this array and convert them into numbers one by one.

var arr1 = [1,2,3];
var arr2 = [4,5,6,7,8,9];
var arr3 = ((",")+","+(",")).split(",");
for(var i=0;i<;i++){
arr3[i] = +arr3[i];
}
(arr3);

Extracurricular extension: Inheritance version

var arr1 = [1,2,3];
var arr2 = [4,5,6,7,8,9];
 = function(arr){
var arr3 = [];
for(var i=0;i<;i++){
arr3[i] = this[i];
}
for(var i=0;i<;i++){
(arr[i]);
}
return arr3;
}
((arr2));

The above is the relevant knowledge about JavaScript analog combination and concat introduced to you by the editor. I hope it will be helpful to everyone!