如何在javascript中计算字符串的行数

Question

I want to count the number of lines in a string

i tried to use this stackoverflow answer :

lines = str.split("\r\n|\r|\n"); 
return  lines.length;

on this string(which was originally a buffer):

 GET / HTTP/1.1
 Host: localhost:8888
 Connection: keep-alive
 Cache-Control: max-age=0
 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_7_2) AppleWebKit/535.2 (KHTML,like Gecko) Chrome/15.0.874.121 Safari/535.2
 Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
 Accept-Encoding: gzip,deflate,sdch
 Accept-Language: en-US,en;q=0.8
 Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3

and for some reason i got lines='1'.

any idea how to make it work?

Answer 1

Using a regular expression you can count the number of lines as

 str.split(/\r\n|\r|\n/).length

Alternately you can try split method as below.

var lines = $("#ptest").val().split("\n");  
alert(lines.length);

working solution: http://jsfiddle.net/C8CaX/

Answer 2

另一个简短的，可能比拆分性能更高的解决方案是：

const lines = (str.match(/\n/g) || '').length + 1

Answer 3

要使用正则表达式进行拆分，请使用/.../

lines = str.split(/\r\n|\r|\n/); 

Answer 4

Hmm yeah... what you're doing is absolutely wrong. When you say str.split("\\r\\n|\\r|\\n") it will try to find the exact string "\\r\\n|\\r|\\n" . That's where you're wrong. There's no such occurance in the whole string. What you really want is what David Hedlund suggested:

lines = str.split(/\r\n|\r|\n/);
return lines.length;

The reason is that the split method doesn't convert strings into regular expressions in JavaScript. If you want to use a regexp, use a regexp.

Answer 5

I made a performance test comparing split with regex, with a string and doing it with a for loop.

It seems that the for loop is the fastest.

NOTE: this code 'as is' is not useful for windows nor macos endline, but should be ok to compare performance.

Split with string:

split('\n').length;

Split with regex:

split(/\n/).length;

Split using for:

var length = 0;
for(var i = 0; i < sixteen.length; ++i)
  if(sixteen[i] == s)
    length++;

http://jsperf.com/counting-newlines/2

Answer 6

There are three options:

Using jQuery (download from jQuery website ) - jquery.com

var lines = $("#ptest").val().split("\n");
return lines.length;

Using Regex

var lines = str.split(/\r\n|\r|\n/);
return lines.length;

Or, a recreation of a for each loop

var length = 0;
for(var i = 0; i < str.length; ++i){
    if(str[i] == '\n') {
        length++;
    }
}
return length;

Answer 7

Better solution, as str.split("\\n") function creates new array of strings split by "\\n" which is heavier than str.match(/\\n\\g). str.match(/\\n\\g) creates array of matching elements only. Which is "\\n" in our case.

var totalLines = (str.match(/\n/g) || '').length + 1;

Answer 8

 <script type="text/javascript">
      var multilinestr = `
        line 1
        line 2
        line 3
        line 4
        line 5
        line 6`;
      totallines = multilinestr.split("\n");
lines = str.split("\n"); 
console.log(lines.length);
</script>

thats works in my case

Answer 9

Another solution for this problem using the spread operator and no regular expressions would be:

const lines = [...csv].reduce((a, c) => a + (c === '\n' ? 1 : 0), 0)

 const csv = ` demo_budget_2021_v4_wk_9,test,Civil,Spares,test,false,12,2021,100 demo_budget_2021_v4_wk_9,test,Civil,Spares,test,false,11,2021,100 demo_budget_2021_v4_wk_9,test,Civil,Spares,test,false,10,2021,100 demo_budget_2021_v4_wk_9,test,Civil,Spares,test,false,9,2021,100 ` const lines = [...csv].reduce((a, c) => a + (c === '\\n' ? 1 : 0), 0) console.log(lines);

Answer 10

Here is the working sample fiddle

Just remove additional \\r\\n and "|" from your reg ex.

Answer 11

I was testing out the speed of the functions, and I found consistently that this solution that I had written was much faster than match ing. We check the new length of the string as compared to the previous length.

const lines = str.length - str.replace(/\n/g, "").length+1;

 let str = `Line1 Line2 Line3`; console.time("LinesTimer") console.log("Lines: ",str.length - str.replace(/\\n/g, "").length+1); console.timeEnd("LinesTimer")