How javascript should create an array

How to create an array in javascript: 1. Use the array literal "[]", the syntax "var a=[value list];", the value list is empty, or it can be multiple separated by "," value; 2. Use "new Array()" to construct an array, the syntax is "var a=new Array (value list);".

The operating environment of this tutorial: windows7 system, javascript version 1.8.5, Dell G3 computer.

Two ways to create an array in javascript

• "Array direct quantity"

• "Array() function"

1. Array direct quantity"[ ]”

1) We can directly use “[]” to assign a value to a variable, in “[]” It can be empty, then define an empty array:

var a = [];  //空数组

Use the length property of the array to get the length of the array, and the return value will be 0.

console.log(a.length);

At this time we can use the form array name[subscript]=value to assign a value to the empty array

a[0]=1;
a[1]="hello";

The array subscript can not only be a number, but also a text string, then the array is an associative array

a["姓名"]="张三";
a["年龄"]=23;

If the subscript value of the array exceeds the range, such as a negative number, floating point number, Boolean value, object or other value, JavaScript will automatically convert it to a string and define it as an associative array.

2)You can also directly define and initialize the array

Contain multiple values ​​directly in "[]" List, separated by commas.

var a = [1, 2, 3];  //包含具体元素的数组

Use the length attribute of the array to obtain the length of the array. The return value is the specifically defined number of array elements.

2. Use new Array() to construct the array

1) If you call the Array() function directly without passing parameters, you can create an empty array.

var a = new Array();  //空数组

Use the length property of the array to get the length of the array, and the return value will be 0.

2) If you pass multiple values ​​(separated by commas) when calling the Array() function, you can create a real array.

var a = new Array(1,2,3);

3)If only one numeric parameter is passed when calling the Array() function, it means that only the length of the array is defined, that is, the number of elements included; the array element is empty , the default value of each element is undefined. (The element values ​​in the array are not defined. Syntactically, elements without any value between two commas are called gap elements)

var a = new Array(3);

Contains an or An array with multiple gap elements is also called a gap array.

[Recommended learning: javascript advanced tutorial]

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