Understanding of js arrays

Array (Array) is an object, which is similar in function to our ordinary objects and is also used to store some values.The difference is that ordinary objects use strings as property names, while arrays use numbers as index operation elements.

Index:

The integer starting from 0 is the index. The storage performance of arrays is better than that of ordinary objects. In development, we often use arrays to store some data.

Array objects are created by adding elements:Create array object syntax:Syntax 1: var arr = new Array();Syntax 2: var arr = []; When using typeof to check an array, it will return the object type.Elements in an array can be of any data type.The elements in the array are separated by .The difference between grammar 1 and grammar 2.var arr = new Array(10); var arr = [10];Syntax 1 creates an array arr with an array length of 10, and syntax 2 creates an array with an element of 10.

Add array element:

Syntax: arr[index value]=data value; such as: arr[0]=1;arr[1]=1;

Read elements in an array syntax:

Syntax: array[index].If reading an index that does not exist, it will not report an error but return undefined.

Get the length of the array:

Syntax: array.length; such as: arr.length.

Modify the length of the array

If the modified length is greater than the original length, the extra part will be vacated.

If the modified length is less than the original length, the extra elements will be deleted.

Add an element to the array

Syntax: array[array.length]=value;

2D array

When we add elements to an array as an array, the array is called a two-dimensional array.

array method

Method	Description	How to use
concat()	Concatenates two or more arrays and returns the result.	Original array name.concat(connection array name);
join()	Puts all elements of the array into a string.Elements are split by the specified separator.	Array name.join("Separator");
pop()	Remove and return the last element of the array.	ArrayName.pop();
push()	Adds one or more elements to the end of the array and returns the new length.	Array name.push("Add element");
reverse()	Reverses the order of elements in the array.	ArrayName.reverse();
shift()	Remove and return the first element of the array.	ArrayName.shift();
slice()	Returns the selected element from an existing array.	s array name.slice(x,y); x is the starting position, y is the accommodation position.
sort()	Sorts the elements of the array.	ArrayName.sort(); This method sorts alphabetically and as a string.
splice()	Remove elements and add new elements to the array.	Array name.splice(x,y,"add element"); x is the position to add new elements, y is to delete several elements.
toString()	Converts the array to a string and returns the result.	ArrayName.toString(); This method returns an array as a comma-separated string
unshift()	Adds one or more elements to the beginning of the array and returns the new length.	Array name.unshift("Add element");
valueOf()	Returns the original value of the array object.	ArrayName.valueOf(); The return result is the same as the original array.

More other ways to view the array:

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