blocks|key|1888981|text|"vanilla“nodeJS+(v0.10.28)中的最大字符串大小约为1+1GB。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1888982|如果您很着急，您可以使用自加倍字符串测试支持的最大字符串大小。测试的系统有8+8GB的RAM，大部分是未使用的。|1888983|x+=+'x';
while+(1){+
+++++x+=+''%2Bx%2Bx;+//+string+context
+++++console.log(x.length);
}

2
4
8
16
32
64
128
256
512
1024
2048
4096
8192
16384
32768
65536
131072
262144
524288
1048576
2097152
4194304
8388608
16777216
33554432
67108864
134217728
268435456
536870912
FATAL+ERROR:+JS+Allocation+failed+-+process+out+of+memory
Aborted+(core+dumped)|code-block|syntax|javascript|1888984|在另一个测试中，我使用for循环一次一个字符达到了1,000,000,000。|1888985|现在，评论家可能会说，“等等，JSON呢?问题是关于JSON的！”我要说的是，JAVASCRIPT中没有JSON对象，JS类型有Object、Array、String、Number等。由于JSON是一个字符串表示，这个问题可以归结为允许的最长字符串。但为了仔细检查，让我们添加一个JSON.stringify调用来处理JSON转换。|1888986|代码|1888987|x+=+'x';
while+(1){+
+++++x+=+''%2Bx%2Bx;+//+string+context
+++++console.log(JSON.stringify({a:x}).length);
}|1888988|期望:+JSON字符串的大小将从2开始，因为第一个对象将字符串表示为'{"a":"xx"}‘，持续10个字符。在属性a中的x字符串变得更大之前，它不会开始加倍。它可能会在2.56亿左右失败，因为它可能会在字符串化中复制第二个副本。回想一下，字符串化独立于原始对象。|1888989|结果：|1888990|10
12
16
24
40
72
136
264
520
1032
2056
4104
8200
16392
32776
65544
131080
262152
524296
1048584
2097160
4194312
8388616
16777224
33554440
67108872
134217736
268435464|1888991|和预期的差不多……|1888992|现在这些限制可能与在nodeJS项目中实现JS的C/C%2B%2B代码有关，此时我相信这与Chrome浏览器中使用的V8代码是相同的。|1888993|博客文章中有证据表明，人们重新编译nodeJS以绕过旧版本的内存限制。还有许多nodejs命令行开关。我还没有测试过这一切的效果。|1888994|entityMap^0|0|0|0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|14|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|15|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|16|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|17|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|18|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|19|8|@]|9|@]|A|$]]|$1|O|3|P|5|F|7|1A|8|@]|9|@]|A|$G|H]]|$1|Q|3|R|5|6|7|1B|8|@]|9|@]|A|$]]|$1|S|3|T|5|6|7|1C|8|@]|9|@]|A|$]]|$1|U|3|V|5|F|7|1D|8|@]|9|@]|A|$G|H]]|$1|W|3|X|5|6|7|1E|8|@]|9|@]|A|$]]|$1|Y|3|Z|5|6|7|1F|8|@]|9|@]|A|$]]|$1|10|3|11|5|6|7|1G|8|@]|9|@]|A|$]]|$1|12|3|-4|5|6|7|1H|8|@]|9|@]|A|$]]]|13|$]]

The maximum string size in "vanilla" nodeJS (v0.10.28) is in the ballpark of 1GB. 

If your are in a hurry, you can test the maximum supported string size with a self doubling string. The system tested has 8GB of RAM, mostly unused.

<pre><code>x = 'x';
while (1){ 
 x = ''+x+x; // string context
 console.log(x.length);
}

2
4
8
16
32
64
128
256
512
1024
2048
4096
8192
16384
32768
65536
131072
262144
524288
1048576
2097152
4194304
8388608
16777216
33554432
67108864
134217728
268435456
536870912
FATAL ERROR: JS Allocation failed - process out of memory
Aborted (core dumped)
</code></pre>

In another test I got to 1,000,000,000 with a one char at a time for loop.

Now a critic might say, "wait, what about JSON. the question is about JSON!" and I would shout THERE ARE NO JSON OBJECTS IN JAVASCRIPT the JS types are Object, Array, String, Number, etc.... and as JSON is a String representation this question boils down to what is the longest allowed string. But just to double check, let's add a JSON.stringify call to address the JSON conversion.

Code

<pre><code>x = 'x';
while (1){ 
 x = ''+x+x; // string context
 console.log(JSON.stringify({a:x}).length);
}
</code></pre>

Expectations: the size of the JSON string will start greater than 2, because the first object is going to stringify to '{"a":"xx"}' for 10 chars. It won't start to double until the x string in property a gets bigger. It will probably fail around 256M since it probably makes a second copy in stringification. Recall a stringification is independent of the original object. 

Result:

<pre><code>10
12
16
24
40
72
136
264
520
1032
2056
4104
8200
16392
32776
65544
131080
262152
524296
1048584
2097160
4194312
8388616
16777224
33554440
67108872
134217736
268435464
</code></pre>

Pretty much as expected....

Now these limits are probably related to the C/C++ code that implements JS in the nodeJS project, which at this time I believe is the same V8 code used in Chrome browsers.

There is evidence from blog posts of people recompiling nodeJS to get around memory limits in older versions. There are also a number of nodejs command line switches. I have not tested the effect of any of this.

blocks|key|1889180|text|这是一个很好的问题，但我认为您需要担心的上限不涉及最大JSON字符串大小。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1889181|在我看来，您需要担心的限制是，当请求线程处理用户的请求时，您希望阻塞请求线程多长时间。|1889182|任何超过1MB的字符串大小都会花费用户几秒钟的时间来上传，10兆字节的字符串可能需要几分钟的时间。收到请求后，服务器需要几百毫秒到几秒的时间来解析成数据结构，这会导致非常差的用户体验(解析JSON非常昂贵)|1889183|带宽和服务器处理时间将掩盖JSON对字符串大小的任何限制。|1889184|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|J|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|K|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|L|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|M|8|@]|9|@]|A|$]]|$1|H|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|I|$]]

This is a good question, but I think the upper limit you need to be worried about doesn't involve the max JSON string size.

In my opinion the limit you need to worry about is how long do you wish to block the request thread while it's processing the user's request. 

Any string size over 1MB will take the user a few seconds to upload and 10 of Megabytes could take minutes. After receiving the request, the server will take a few hundred milliseconds to seconds to parse into a data structure leading to a very poor user experience (Parsing JSON is very expensive)

The bandwidth and server processing times will overshadow any limit JSON may have on string size.

blocks|key|1675271|text|node.js中字符串的最大长度是由底层的Javascript引擎"V8“定义的。在V8中，最大长度与堆大小无关。字符串的大小实际上受到优化对象布局定义的限制的约束。参见https://chromium-review.googlesource.com/c/v8/v8/%2B/2030916，这是最近(2020年2月)对V8中字符串的最大长度的更改。提交消息解释了随时间变化的不同长度。限制从大约256MB到1+1GB，然后又回到512MB+(在64位V8平台上)。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1675272|entityMap|0|LINK|mutability|MUTABLE|url|https://chromium-review.googlesource.com/c/v8/v8/%2B/2030916^0|2D|1M|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

The maximum length of a string in node.js is defined by the underlying Javascript Engine "V8". In V8 the maximum length is independent of the heap size. The size of a string is actually constrained by the limits defined by optimized object layout. See <a href="https://chromium-review.googlesource.com/c/v8/v8/+/2030916" rel="nofollow noreferrer">https://chromium-review.googlesource.com/c/v8/v8/+/2030916</a> which is a recent (Feb 2020) change to the maximum length of a string in V8. The commit message explains the different lengths over time. The limit has gone from about 256MB to 1GB then back to 512MB (on 64-bit V8 platforms).

A section of my Node.js application involves receiving a string as input from the user and storing it in a JSON file. JSON itself obviously has no limit on this, but is there any upper bound on the amount of text that Node can process into JSON?

Note that I am not using MongoDB or any other technology for the actual insertion - this is native stringification and saving to a .json file using <code>fs</code>.

Is there a limit on the size of a string in JSON with Node.js?

数据结构

服务器

MongoDB

JSON

我的Node.js应用程序的一部分涉及从用户接收一个字符串作为输入，并将其存储在一个JSON文件中。JSON本身显然对此没有限制，但是Node可以处理成JSON的文本数量有上限吗？请注意，我没有使用MongoDB或任何其他技术进行实际插入-这是本机字符串化，并使用fs保存到.json文件。

问在使用Node.js的JSON中，字符串的大小有限制吗？
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