Common methods for sharing strings in JavaScript (with code)

In JavaScript, it is often necessary to process strings, such as obtaining the length of a string, intercepting a string, converting a string into an array, etc. This article mainly focuses on strings and mainly introduces the common strings. processing method. Friends in need can take a look.

1. Get the actual length of the string

 var jmz = {}; 
function strlen(str) {
    ///<summary>获得字符串实际长度，中文2，英文1</summary>
    ///<param name="str">要获得长度的字符串</param>
    var realLength = 0, len = str.length, charCode = -1;
    for (var i = 0; i < len; i++) {
        charCode = str.charCodeAt(i);
        if (charCode >= 0 && charCode <= 128) realLength += 1;
        else realLength += 2;
    }
    return realLength;
};

2. Intercept the difference between the substr and substring methods of the string

substr method

Returns a substring of the specified length starting at the specified position.
stringvar.substr(start [, length ])

Parameters
stringvar: required. The string literal or String object from which the substring is to be extracted.
start: required option. The starting position of the desired substring. The first character in the string has index 0.
length: optional. The number of characters that should be included in the returned substring.

Description
If length is 0 or a negative number, an empty string will be returned. If this parameter is not specified, the substring will be continued to the end of stringvar.

Example
The following example demonstrates the use of the substr method.

function SubstrDemo(){
   var s, ss;                // 声明变量。
   var s = "The rain in Spain falls mainly in the plain.";
   ss = s.substr(12, 5); // 获取子字符串。
   return(ss);               // 返回 "Spain"。
}

substring method

Returns the substring located at the specified position in the String object.

strVariable.substring(start, end)
"String Literal".substring(start, end)

Parameters
start: Indicates the starting position of the substring, the index starts from 0.

end: Indicates the end position of the substring, the index starts from 0.

Description
The substring method will return a string containing the substring from start to the end (excluding end).
The substring method uses the smaller of start and end as the starting point of the substring. For example, strvar.substring(0, 3) and strvar.substring(3, 0) will return the same substring.

If start or end is NaN or a negative number, replace it with 0.
The length of the substring is equal to the absolute value of the difference between start and end. For example, in strvar.substring(0, 3) and strvar.substring(3, 0) the length of the substring returned is 3.

Example
The following example demonstrates the use of the substring method.

function SubstringDemo(){
   var ss;                         // 声明变量。
   var s = "The rain in Spain falls mainly in the plain..";
   ss = s.substring(12, 17);   // 取子字符串。
   return(ss);                     // 返回子字符串。
}

3. Remove spaces from strings

Delete all spaces in the string

  function trim(str){
    return str.replace(/[ ]/g,""); //去除字符算中的空格
    }

Deleted characters count as spaces on the left and right sides, and do not delete characters Change the spaces inside

   function leftright(str){
    return str.replace(/(^\s*)|(\s*$)/g,""); //去除字符窜的左右空格
   }

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