Summary of methods for obtaining the number of bytes in a string using js

This article mainly introduces the js method of obtaining string bytes. The example summarizes the related techniques of javascript string length calculation. Friends who need it can refer to it

The example in this article describes the method of obtaining the number of bytes in a string using js. Share it with everyone for your reference. The details are as follows:

As we all know, length can be used to obtain the length of a string.
So what about getting the number of bytes of this string?

English letters must have the same length and number of bytes: both are 1
And Chinese length=1, number of bytes=2
Therefore, what needs to be done is to change the number of bytes of Chinese characters Calculated.

Method one:

alert('a'.replace(/[^\u0000-\u00ff]/g,"aaa").length); 
//原理：把中文字符替换成2个英文字母，那么字节数就是2，
//示例中改成替换成3个英文字母了。
//因此弹出的字节数是3，如果要正确的，当然是替换成2个字母了
//\u0000这个表示的是unicode编码

Method two:

var str='我我我';
var bytesCount;
for (var i = 0; i < str.length; i++)
{
  var c = str.charAt(i);
  if (/^[\u0000-\u00ff]$/.test(c)) //匹配双字节
  {
  bytesCount += 1;
  }
  else
  {
  bytesCount += 2;
  }
}
alert(bytesCount);
//结果是6
//原理也很简单，用正则判断是不是中文，如果是的话，字节数就加1。

Regular expression matching Chinese characters: [\u4e00-\u9fa5]

Matches double-byte characters (including Chinese characters): [^\x0000-\x00ff]

can be used to calculate the length of a string (a double-byte character is counted as 2, and ASCII characters are counted as 1) Several functions in

JS:

charAt(num) //Get the character at the num position of the string
charCodeAt(num)// Get the unicode encoding of the character at the num position of the string
fromCharCode(num)//Get the character corresponding to the unicode encoding

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