A simple example of js intercepting fixed-length Chinese and English characters_javascript skills

Although js provides a function for calculating the number of bytes occupied by a string, it cannot correctly calculate the number of bytes occupied by Chinese characters, such as document.form1.username.value="I am Chinese",document.form1.username. value.length returns 5 instead of 10, which brings some troubles to programming, such as limiting the input of fixed-length characters and intercepting fixed-length strings. Because of this problem, the expected effect cannot be achieved. The following is what I wrote. A simple function, used to intercept fixed-length strings, applicable to both Chinese and English. If there is anything wrong, please correct me!

Copy code The code is as follows:

//js intercepts strings, both Chinese and English can be used
//If the given string is greater than the specified length, intercept the specified length and return it, otherwise return the source string.
function cutstr(str,len)
{
var str_length = 0;
var str_len = 0;
str_cut = new String();
str_len = str.length;
for(var i = 0;i {
a = str.charAt(i);
str_length ;
if(escape(a).length > 4 )
{
//The length of Chinese characters after encoding is greater than 4
str_length ;
}
str_cut = str_cut.concat(a);
if(str_length&g t;=len)
                                                                                                                                                                                                                                             Source string;
if(str_length return str;
}
}