javascript javascript中不同数据类型的内存使用情况
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Memory Usage Of Different Data Types in javascript
提问by A.B.Developer
A question that has happened to me is that different Data type in javascript how many use of memory . for Example in C++ data type like int , char , float uses order 2 , 1 , 8 byte of memory . now data Type like Number , string , boolean , null , undefind and Objects , Arrays in javascript how many use of memory and what is ranges that accepted ? Accept my apologize because of my low English level!!!
我遇到的一个问题是 javascript 中的不同数据类型有多少内存使用。例如在 C++ 数据类型中，如 int 、 char 、 float 使用顺序 2 、 1 、 8 字节的内存。现在数据类型如数字、字符串、布尔值、空值、未定义和对象，javascript 中的数组有多少内存使用以及接受的范围是多少？接受我的道歉，因为我的英语水平低！！！
采纳答案by Rani Kheir
Numbers are 8 bytes.
数字是 8 个字节。
Found that in this w3schools page.
在这个w3schools 页面中发现。
I searched around a bit more for other JavaScript primitive types, but it's surprisingly hard to find this information! I did find the following code though:
我搜索了更多其他 JavaScript 原始类型，但很难找到这些信息！我确实找到了以下代码：
...
if ( typeof value === 'boolean' ) {
bytes += 4;
}
else if ( typeof value === 'string' ) {
bytes += value.length * 2;
}
else if ( typeof value === 'number' ) {
bytes += 8;
}
...
Seems to indicate that a String is 2 bytes per character, and a boolean is 4 bytes.
似乎表明一个字符串是每个字符 2 个字节，一个布尔值是 4 个字节。
Found that code hereand here. The full code's actually used to get the rough size of an object.
在此处和此处找到该代码。完整的代码实际上用于获取对象的粗略大小。
Although, upon further reading, I found this interesting code by konijnon this page: Count byte length of string.
虽然，在进一步阅读后，我在此页面上发现了konijn 的这个有趣的代码：Count byte length of string。
function getByteCount( s )
{
var count = 0, stringLength = s.length, i;
s = String( s || "" );
for( i = 0 ; i < stringLength ; i++ )
{
var partCount = encodeURI( s[i] ).split("%").length;
count += partCount==1?1:partCount-1;
}
return count;
}
getByteCount("i?js"); // 6 bytes
getByteCount("abcd"); // 4 bytes
So it seems that the string's size in memory depends on the characters themselves. Although I am still trying to figure out why he set the count to 1 if it's 1, otherwise he took count-1(in the for loop).
所以似乎字符串在内存中的大小取决于字符本身。尽管我仍在试图弄清楚为什么如果计数为 1，他将计数设置为 1，否则他count-1（在 for 循环中）接受了。
Will update post if I find anything else.
如果我发现其他任何东西，将更新帖子。
回答by superjos
As of today, MDN Data Structurespage gives some more info about it:
截至今天，MDN 数据结构页面提供了有关它的更多信息：
Number
数字
According to the ECMAScript standard, there is only one number type: the double-precision 64-bit binary format IEEE 754 value
根据 ECMAScript 标准，只有一种数字类型：双精度 64 位二进制格式 IEEE 754 值
So that should amount to 8 bytes.
所以这应该是 8 个字节。
String
细绳
JavaScript's String type is used to represent textual data. It is a set of "elements" of 16-bit unsigned integer values.
JavaScript 的 String 类型用于表示文本数据。它是一组 16 位无符号整数值的“元素”。
So that should amount to 2 bytes per character.
所以这应该相当于每个字符 2 个字节。
Boolean
布尔值
Boolean represents a logical entity and can have two values: true, and false.
Boolean 代表一个逻辑实体，可以有两个值：true 和 false。
Nothing more about that.
仅此而已。
