Array-白红宇

Array

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发布时间：2019-06-27

本文共 4104 字，大约阅读时间需要 13 分钟。

n JavaScript, the Array property of the global object is a constructor for array instances.(在JavaScript,全局对象数组属性是构造数组对象的构造器。)

An array is a JavaScript object. Note that you shouldn't use it as an associative array, use Object instead.(一个数组是JavaScript对象。注意你不应该把它作为关联数组来使用，应该使用对象来代替。)

Creating an Array(创建数组)

The following example creates an array, msgArray, with a length of 0, then assigns values to msgArray[0] and msgArray[99], changing the length of the array to 100.(下面的例子创建了一个长度为0的数组msgArray，然后把数值赋给msgArray[0]到msgArray[99],把数组的长度改变成100。)

<script>

var msgArray = new Array();

msgArray[0] = "Hello";

msgArray[99] = "world";

if (msgArray.length == 100){

document.write("The length is 100.");

}

</script>

Creating a Two-dimensional Array(创建一个二维数组)

The following creates chess board as a two dimensional array of strings.(下面的例子创建了二维字符串数组来表示国际象棋棋盘) The first move is made by copying the 'P' in 6,4 to 4,4. The position 6,4 is left blank.(第一步是拷贝6,4的'P'到4,4。位置6,4是空白的)

<script>

var board =

[ ['R','N','B','Q','K','B','N','R'],

['P','P','P','P','P','P','P','P'],

[' ',' ',' ',' ',' ',' ',' ',' '],

[' ',' ',' ',' ',' ',' ',' ',' '],

[' ',' ',' ',' ',' ',' ',' ',' '],

[' ',' ',' ',' ',' ',' ',' ',' '],

['p','p','p','p','p','p','p','p'],

['r','n','b','q','k','b','n','r']];

document.write(board.join('\n') + '\n\n' + "<br/>");

// Move King's Pawn forward 2

board[4][4] = board[6][4];

board[6][4] = ' ';

document.write(board.join('\n'));

</script>

Here is the output:(下面是输出:)

R,N,B,Q,K,B,N,R

P,P,P,P,P,P,P,P

, , , , , , ,

p,p,p,p,p,p,p,p

r,n,b,q,k,b,n,r

R,N,B,Q,K,B,N,R

P,P,P,P,P,P,P,P

, , , , , , ,

, , , ,p, , ,

, , , , , , ,

p,p,p,p, ,p,p,p

r,n,b,q,k,b,n,r

Accessing array elements(访问数组元素)

Array elements are nothing less than object properties, so they are accessed as such.(数组元素和对象属性是一样的，所以它们是这样被访问的。)

<script>

var myArray = new Array("Wind", "Rain", "Fire");

document.write(myArray[0] + "<br/>"); // "Wind"

document.write(myArray[1] + "<br/>"); // "Rain"

// etc.

document.write(myArray.length + "<br/>"); // 3

// Even if indices are properties, the following notation throws a syntax error(即使索引是属性，下面符号将会抛出语法错误)

//document.write(myArray.2 + "<br/>");

// It should be noted that in JavaScript, object property names are strings. Consequently,

//应该注意的是，在JavaScript中，对象的属性名称是字符串。因此，

document.write((myArray[0] === myArray["0"]) + "<br/>");

document.write((myArray[1] === myArray["1"]) + "<br/>");

// etc.

// However, this should be considered carefully(无论如何，这都要仔细地思考)

document.write(myArray[02] + "<br/>"); // "Fire". The number 02 is converted as the "2" string

document.write(myArray["02"] + "<br/>"); // undefined. There is no property named "02"

</script>

Relationship between length and numerical properties(长度和数值属性们的关系)

An array's length property and numerical properties are connected. (数组长度属性和数值属性是关联的)Here is some code explaining how this relationship works.(下面这些代码解释了这些关系是怎么工作的。)

<script>

var a = [];

a[0] = 'a';

console.log(a[0]); // 'a'

console.log(a.length); // 1

a[1] = 32;

console.log(a[1]); // 32

console.log(a.length); // 2

a[13] = 12345;

console.log(a[13]); // 12345

console.log(a.length); // 14

a.length = 10;

console.log(a[13]); // undefined, when reducing the length elements after length+1 are removed

console.log(a.length); // 10

</script>

Creating an array using the result of a match(使用match的结果创建对象)

The result of a match between a regular expression and a string can create an array. (正则表达式和字符串的match的结果可以创建一个字符串。)This array has properties and elements that provide information about the match.(这个数组有能提供关于这个match的信息的属性和元素。) An array is the return value of RegExp.exec, String.match, and String.replace.(RegExp.exec,String.match,String.replace返回了数组) To help explain these properties and elements, look at the following example and then refer to the table below:(为了解释这些属性和元素，请看下面的例子，接下来看看下面的表格：)